bevy_reflect: Add crate level functions feature docs

[nixpulvis]

Adds the missing section for the functions cargo feature of the bevy_reflect crate.

[nixpulvis]

@MrGVSV perhaps you have a solution to the issue currently here. I've linked to the relevant module docs and types within the func module, however, since they will not be present without the feature, this will lead to broken links.

Do you have thoughts on how to make this more discoverable, especially on sites like docs.rs, which don't compile with features enabled?

[MrGVSV]

@MrGVSV perhaps you have a solution to the issue currently here. I've linked to the relevant module docs and types within the func module, however, since they will not be present without the feature, this will lead to broken links.

Do you have thoughts on how to make this more discoverable, especially on sites like docs.rs, which don't compile with features enabled?

Pretty sure bevy_reflect builds with all features enabled, so it shouldn't be an issue.

I think the CI error is related to referencing DynamicClosure, which no longer exists.

[alice-i-cecile]

Happy to merge this in 0.15 if it's ready, but I'm not comfortable blocking the release on it :) Le me know if you need a hand!

[nixpulvis]

Oh totally forgot about this. I’m out tonight, but I’ll look back it this tomorrow.