Update master branch README.md

Author: onnimonni

_config/README.md

@@ -4,6 +4,8 @@ This is the static html for https://wp-languages.github.io. The site provides Wo
 
 See [src](https://github.com/wp-languages/wp-languages.github.io) branch for source code.
 
+**Note:** Pull requests are not accepted into this branch. Create them into [src](https://github.com/wp-languages/wp-languages.github.io) branch instead.
+
 ## License
 MIT