docs: add credits, update license year

Author: adhocore

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2017 Jitendra Adhikari
+Copyright (c) 2017-2020 Jitendra Adhikari
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -601,7 +601,7 @@ appname subcommand <tab> # autocompletes options for subcommand (phint init <tab
 
 ## License
 
-> &copy; 2018, [Jitendra Adhikari](https://github.com/adhocore) | [MIT](./LICENSE)
+> &copy; 2017-2020, [Jitendra Adhikari](https://github.com/adhocore) | [MIT](./LICENSE)
 
 ### Credits