Address grpc-community master to main branch rename (grpc#723)

Author: chalin

CONTRIBUTING.md

@@ -1,5 +1,5 @@
 # How to contribute
 
 We definitely welcome patches and contributions to grpc.io! Please read the gRPC
-organization's [governance rules](https://github.com/grpc/grpc-community/blob/master/governance.md)
-and [contribution guidelines](https://github.com/grpc/grpc-community/blob/master/CONTRIBUTING.md) before proceeding.
+organization's [governance rules](https://github.com/grpc/grpc-community/blob/main/governance.md)
+and [contribution guidelines](https://github.com/grpc/grpc-community/blob/main/CONTRIBUTING.md) before proceeding.

GOVERNANCE.md

@@ -1 +1 @@
-This repository is governed by the gRPC organization's [governance rules](https://github.com/grpc/grpc-community/blob/master/governance.md).
+This repository is governed by the gRPC organization's [governance rules](https://github.com/grpc/grpc-community/blob/main/governance.md).

MAINTAINERS.md

@@ -20,5 +20,5 @@ The emeritus maintainers of this repository (in alphabetical order) are:
 - If you were a maintainer and would like to add your name to the emeritus list,
   submit a PR.
 
-[grpc/grpc-community/governance.md]: https://github.com/grpc/grpc-community/blob/master/governance.md
-[grpc/grpc-community/CONTRIBUTING.md]: https://github.com/grpc/grpc-community/blob/master/CONTRIBUTING.md
+[grpc/grpc-community/governance.md]: https://github.com/grpc/grpc-community/blob/main/governance.md
+[grpc/grpc-community/CONTRIBUTING.md]: https://github.com/grpc/grpc-community/blob/main/CONTRIBUTING.md

content/en/blog/hello-pancakes.md

@@ -8,18 +8,18 @@ author:
 
 Dear gRPC,
 
-We messed up. We are so sorry that we missed your birthday this year. Last year we celebrated [with cake](https://twitter.com/grpcio/status/968618209803931648) and fanfare, but this year we dropped the ball. Please don't think that we love you any less. 
+We messed up. We are so sorry that we missed your birthday this year. Last year we celebrated [with cake](https://twitter.com/grpcio/status/968618209803931648) and fanfare, but this year we dropped the ball. Please don't think that we love you any less.
 
-You're 4 now and that's a big milestone! You're part of so much amazing technology at companies like Salesforce, Netflix, Spotify, Fanatics, and of course, Google. In fact just this week the [biggest API Google has](https://ads-developers.googleblog.com/2019/03/upgrade-to-new-google-ads-api-to-get.html) went production-ready with gRPC. 
+You're 4 now and that's a big milestone! You're part of so much amazing technology at companies like Salesforce, Netflix, Spotify, Fanatics, and of course, Google. In fact just this week the [biggest API Google has](https://ads-developers.googleblog.com/2019/03/upgrade-to-new-google-ads-api-to-get.html) went production-ready with gRPC.
 
 We're proud of you, gRPC, and we're going to make this up to you. For starters - we got you a puppy! He's an adorable **G**olden **R**etriever and his name is **P**an**C**akes. He loves to run back and forth with toys, packets, or messages. He's super active and no matter how much we train him, we just can't get him to REST. PanCakes is going to be your best friend, and ambassador.
 
-![gRPC Mascot PanCakes](https://raw.githubusercontent.com/grpc/grpc-community/master/PanCakes/Pancakes_Birthday.png)
+![gRPC Mascot PanCakes](https://raw.githubusercontent.com/grpc/grpc-community/main/PanCakes/Pancakes_Birthday.png)
 
-Even though it's a bit late, we still want to throw you a party, gRPC. Our friends at CNCF have planned a [big event](https://events.linuxfoundation.org/events/grpconf-2019/) for you on March 21, and there's going to be lots of people there! They'll be sharing stories about the cool things they've built, and meeting new people. It's an entire day all about you, and everyone there is going to learn so much. There will be other puppies who can play with PanCakes! Some of the amazing dogs from [Canine Companions for Independence](http://www.cci.org/) will be there to greet conference attendees and share how they help their humans live a more independent life. 
+Even though it's a bit late, we still want to throw you a party, gRPC. Our friends at CNCF have planned a [big event](https://events.linuxfoundation.org/events/grpconf-2019/) for you on March 21, and there's going to be lots of people there! They'll be sharing stories about the cool things they've built, and meeting new people. It's an entire day all about you, and everyone there is going to learn so much. There will be other puppies who can play with PanCakes! Some of the amazing dogs from [Canine Companions for Independence](http://www.cci.org/) will be there to greet conference attendees and share how they help their humans live a more independent life.
 
 We are so excited to see what this year holds for you, gRPC!
 
 ~ gRPC Maintainers
 
-![gRPC Mascot PanCakes](https://raw.githubusercontent.com/grpc/grpc-community/master/PanCakes/Pancakes_Birthday_4.png)
+![gRPC Mascot PanCakes](https://raw.githubusercontent.com/grpc/grpc-community/main/PanCakes/Pancakes_Birthday_4.png)

content/en/community/_index.md

@@ -139,8 +139,8 @@ New projects are welcome!][grpc-ecosystem-request].
 [gRFCs]: https://github.com/grpc/proposal
 [gRPC Ecosystem Project Request]: https://docs.google.com/a/google.com/forms/d/119zb79XRovQYafE9XKjz9sstwynCWcMpoJwHgZJvK74
 [gRPC Ecosystem]: https://github.com/grpc-ecosystem
-[grpc-community/CONTRIBUTING.md]: https://github.com/grpc/grpc-community/blob/master/CONTRIBUTING.md
-[grpc-ecosystem-request]: https://github.com/grpc/grpc-community/blob/master/grpc_ecosystem.md
+[grpc-community/CONTRIBUTING.md]: https://github.com/grpc/grpc-community/blob/main/CONTRIBUTING.md
+[grpc-ecosystem-request]: https://github.com/grpc/grpc-community/blob/main/grpc_ecosystem.md
 [grpc-io]: https://groups.google.com/forum/#!forum/grpc-io
 [grpc-org]: https://github.com/grpc
 [grpc-tag]: https://stackoverflow.com/questions/tagged/grpc