Added plugin.proto to well-known types for JS.
Added plugin.proto to well-known types for JS.

google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf