rustdoc: Tracking issue for rustdoc internals

[GuillaumeGomez]

This is a tracking issue for the internal feature rustdoc internals.
The feature gate for this issue is rustdoc_internals.

It hosts the following non-exhaustive list of subfeatures (not guaranteed to be up to date):

• #[doc(keyword = "…")]
  • Initial impl: rustdoc: introduce the #[doc(keyword="")] attribute for documenting keywords #51140
• #[doc(attribute = "…")]
  • Initial impl: Add new doc(attribute = "...") attribute #142472

Note

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.

A tracking issue is however not meant for large scale discussion, questions, or bug reports.
Instead, open a dedicated issue for the specific matter or post in the #t-rustdoc Zulip channel.

Discussion comments will get marked as off-topic or deleted.
Repeated discussions on the tracking issue may lead to the tracking issue getting locked.

[jhpratt]

I thought we didn't need tracking issues for features not intended to be stabilized?