Add micro Registered Extension Number (#9767)

unistack-org/micro (microservices framework) uses protoc-gen-go-micro generator that has extension support for additional framework related options.

It is currently not using any registered extension number, so i want to stabilise this and i think that this is a good thing.

See here for an example of the extenstion in action.

Co-authored-by: Adam Cozzette <acozzette@google.com>

docs/options.md

@@ -308,8 +308,11 @@ with info about your project (name and website) so we can add an entry for you.
 1. Protoc-gen-fieldmask
    * Website: https://github.com/yeqown/protoc-gen-fieldmask
    * Extension: 1142
-
+ 
 1. Google Gnostic
    * Website: https://github.com/google/gnostic
    * Extension: 1143
 
+1. Protoc-gen-go-micro
+   * Website: https://github.com/unistack-org/protoc-gen-go-micro
+   * Extension: 1144