Protocol Buffer text format

[hickford]

Protocol Buffer text format is a data format, typically parsed together with a Protocol Buffers schema. Thus Protocol Buffers text format is to Protocol Buffers as XML is to XSD.

TextMate Grammar by https://github.com/thejustinwalsh/textproto-grammar (MIT licence)

Fixes #5091.

Checklist:

• I am adding a new language.
  • The extension of the new language is used in hundreds of repositories on github.com.
    • Search results for each extension:
      • .pbtxt 2000k hits https://github.com/search?q=extension%3Apbtxt&type=Code
      • .textproto 100k hits https://github.com/search?q=extension%3Atextproto&type=Code
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/google/nvidia_libs_test/blob/master/cudnn_benchmarks.textproto
      • https://github.com/tensorflow/tfx/blob/master/tfx/examples/chicago_taxi_pipeline/data/user_provided_schema/schema.pbtxt
    • Sample license(s): Apache-2.0 License, Apache-2.0 License
  • I have included a syntax highlighting grammar: example

[Alhadis]

First of all, please don't add language_ids manually. These need to be generated by running script/update-ids.

Secondly, how does this format differ from the currently-supported Protocol Buffer language? Is it a different format, or should .pbtxt and .textproto be added to the existing entry's extensions list?
EDIT: Never mind, I posted this before the OP was updated with links to documentation.

[Alhadis]

Looks good to me! 👍 Thanks for the superb contribution!

[lildude]

Looks good, just one request: can you please add a sample for the .pbtxt extension.

[hickford]

Good idea, done.

[Stanzilla]

Could we also get .pbt added?

[lildude]

Sure, though that would now need to be a new PR as I've just merged this one.