chore: add upgrading guide (netlify#201)

* feat: export default config from functions adapter

* chore: add upgrading guide

* chore: remove extraneous change
chore: remove extraneous changes

* chore: update to include re-exported handleRequest

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: ascorbic

docs/upgrading.md

@@ -0,0 +1,123 @@
+# Upgrading from Remix 1 to Remix 2
+
+The Remix docs contain a comprehensive [guide to upgrading your Remix site](https://remix.run/docs/en/main/start/v2)
+from v1 to v2. This guide shows the steps that are specific to upgrading a site on Netlify.
+
+## Update packages
+
+The Netlify packages are now published under the `@netlify` scope. Update your `package.json` to use the new packages:
+
+### Netlify Functions
+
+```diff
+{
+  "dependencies": {
+-   "@remix-run/netlify": "^1.0.0",
++   "@netlify/functions": "^2.0.0",
++   "@netlify/remix-adapter": "^2.0.0",
+  }
+}
+```
+
+Then update all of the other `@remix-run` packages to `^2.0.0`.
+
+### Netlify Edge Functions
+
+```diff
+{
+  "dependencies": {
+-   "@remix-run/netlify-edge": "experimental-netlify-edge",
++   "@netlify/remix-edge-adapter": "^3.0.0",
++   "@remix-run/react": "^2.0.0",
+  }
+}
+```
+
+Then update all of the other `@remix-run` packages to `^2.0.0`.
+
+## Update your `remix.config.js`
+
+The config options have been greatly simplified in v2. Update your `remix.config.js` to use the new options. Use these
+full examples as a reference, ensuring you copy over any customizations you've made to your own config.
+
+### Netlify Functions
+
+```js
+import { config } from '@netlify/remix-adapter'
+
+/** @type {import('@remix-run/dev').AppConfig} */
+export default {
+  ...config,
+  // Add your custom config here.
+}
+```
+
+### Netlify Edge Functions
+
+```js
+import { config } from '@netlify/remix-edge-adapter'
+
+/** @type {import('@remix-run/dev').AppConfig} */
+export default {
+  ...config,
+  // Add your custom config here.
+}
+```
+
+## Update your entrypoint files
+
+The adapter packages now export `handleRequest`, so you can replace the contents of your `app/entry.server.tsx` with the
+following:
+
+### Netlify Functions
+
+```ts
+export { handleRequest as default } from '@netlify/remix-adapter'
+```
+
+### Netlify Edge Functions
+
+```ts
+export { handleRequest as default } from '@netlify/remix-edge-adapter'
+```
+
+## Update your server files
+
+Replace your `server.ts` or `server.js` file with the following files:
+
+### Netlify Functions
+
+- [`server.ts`](https://github.com/netlify/remix-compute/blob/main/packages/demo-site/server.ts)
+
+### Netlify Edge Functions
+
+- [`server.ts`](https://github.com/netlify/remix-compute/blob/main/packages/edge-demo-site/server.ts)
+
+## Update your build commands
+
+Remix 2 includes [greatly improved support](https://remix.run/docs/en/main/start/v2#custom-app-server) for `remix dev`
+with custom servers and runtimes, and the Netlify Edge Function adapter has full support.
+
+You need to update your `dev` command in your `package.json` and `netlify.toml`:
+
+### Netlify Edge Functions
+
+```diff
+{
+  "scripts": {
+-   "dev": "remix dev",
++   "dev": "remix dev --manual -c \"ntl dev --framework=#static\"",
+  }
+}
+```
+
+This means that when you run `npm run dev`, it will start the Remix dev server, and then start the Netlify dev server to
+serve your Edge Functions. This gives full hot updates, while also running through the real Netlify Edge Functions
+runtime.
+
+The other difference is that if you were previously running `netlify dev` as your dev command, you should switch to
+`npm run dev` instead, as the Remix dev server will now start the Netlify dev server for you, instead of vice versa.
+
+### Netlify Functions
+
+No updates are needed here, as it still uses the Node-based Remix dev server.