Include markdown metadata to support entry-points

[ovidner]

The markdown package uses entry-points to allow short names for built-in extensions, such as extra or toc. The hook has been updated so that the necessary package metadata is included in the build, enabling the same behavior as the unfrozen package.

This would resolve problems like Python-Markdown/markdown#884.

[bwoodsend]

I hope that you are aware though that other providers of mardown's entry point will still not be collected.

[bwoodsend]

CI/CD run is here.

[bwoodsend]

Thanks @ovidner!

[ovidner]

I hope that you are aware though that other providers of mardown's entry point will still not be collected.

Ah yes, that's true. I guess that it could be even better to use collect_entry_point("markdown.extensions"), considering that. But for the time being, I think this resolves the biggest issue. At least it's a fix for my own use-case 😁