Update Protobuf support (#2381)

Summary:
**Update protobuf library with new support for `enum` and `oneof` types**

## Changelog

- Update plugin code for library API changes and other cleanup
- Add instructions to readme

Pull Request resolved: https://github.com/facebook/flipper/pull/2381

Test Plan: see demo app at https://github.com/hbmartin/protobuf_java_to_protobufjs

Reviewed By: priteshrnandgaonkar

Differential Revision: D28831035

Pulled By: passy

fbshipit-source-id: 46e196293330b615394606bd3486ea47ad6a0630

docs/setup/network-plugin.mdx

@@ -49,6 +49,25 @@ new OkHttpClient.Builder()
 
 As interceptors can modify the request and response, add the Flipper interceptor after all others to get an accurate view of the network traffic.
 
+### Protobuf / Retrofit Integration
+
+If you are using Retrofit with Protobuf request or response types, you can setup automatic decoding so that the network inspector can display a human readable payload. First you must add the separate dependency:
+
+```groovy
+dependencies {
+  debugImplementation 'com.facebook.flipper:flipper-retrofit2-protobuf-plugin:0.91.2'
+}
+```
+
+Then call `SendProtobufToFlipperFromRetrofit` for each service class.
+
+```kotlin
+import com.facebook.flipper.plugins.retrofit2protobuf.SendProtobufToFlipperFromRetrofit
+
+SendProtobufToFlipperFromRetrofit("https://baseurl.com/", MyApiService::class.java)
+```
+
+
 ## iOS
 
 To enable network inspection, add the following pod to your Podfile: