[docs] update protobuf.js link and formatting

The casing was changed in v5.0 (https://github.com/protobufjs/protobuf.js/wiki/Changes-in-protobuf.js-5.0), and the repository organization was updated at some point.

README.md

@@ -6,11 +6,11 @@
 
 Webpack loader to translate
 [protobuf](https://github.com/google/protobuf/) definitions to
-[ProtoBuf.js](https://github.com/dcodeIO/ProtoBuf.js/)
+[protobuf.js](https://github.com/protobufjs/protobuf.js)
 modules. Equivalent to running your definitions through the [pbjs
 CLI](https://github.com/protobufjs/protobuf.js/tree/master/cli).
 
-This allows you to use the light or minimal ProtoBuf.js distributions
+This allows you to use the light or minimal protobuf.js distributions
 without an explicit compile step in your build pipeline.
 
 # Installation