(protobuf) Should highlight multiline comments as comments

[Paxa]

protobuf supports comments like /* bla bla */, but they are not highlighted

https://developers.google.com/protocol-buffers/docs/proto3#adding-comments

[joshgoebel]

@Paxa Should be a simple one line patch, you up for making a PR?

[joshgoebel]

Ping. @Paxa

[Paxa]

I can try

[joshgoebel]

Awesome. Looking forward to seeing!