Fixes issue where protoc did not recognize plugin.py as win32 application

[boukeversteegh]

Hi~

Thanks for this awesome library!

There's a bug however that I want to look into, but I couldn't run generate on my windows system. This PR fixes that.

When running pyenv run generate on windows, protoc does not accept ../plugin.py as an executable win32 application.

See for example: protocolbuffers/protobuf#3923

This PR adds a .bat file that executes python, which is used when running the generate.py on windows.

[nat-n]

Out of curiosity (since I know very little about windows):

I take it the issue the .bat file solves is windows not understanding the shebang?

Am I correct in thinking this only matters if you're using the --plugin option on the protoc CLI, since if you use the --python_betterproto_out option as in the readme it'll pick up the protoc-gen-python_betterproto console script?

[boukeversteegh]

Out of curiosity (since I know very little about windows):

I take it the issue the .bat file solves is windows not understanding the shebang?

Am I correct in thinking this only matters if you're using the --plugin option on the protoc CLI, since if you use the --python_betterproto_out option as in the readme it'll pick up the protoc-gen-python_betterproto console script?

Yes, this is only needed for development. Since I need this change for every other PR I'm working on, and my next PR also includes it with a refactor, we could drop this PR in favor of: #51

[boukeversteegh]

Closing in favor of #51