ACPs in tracking issue template for rust repository

[clarfonthey]

I figured it would be best to file an issue here, even though it would ultimately result in a PR for the rust repo. When opening up a tracking issue (namely rust-lang/rust#111774), I chose to add the ACP to the Steps / History section. Perhaps this should be part of the standard template, since all tracking issues which didn't start from an RFC (which has a separate template) should include one?

Link to the relevant issue template: https://github.com/rust-lang/rust/blob/master/.github/ISSUE_TEMPLATE/library_tracking_issue.md

In the tracking issue, I also took the liberty of linking this page on ACPs, since there was a similar one linked for FCPs: https://std-dev-guide.rust-lang.org/feature-lifecycle/api-change-proposals.html

[m-ou-se]

Thanks! We're revising the process a bit. We'll make a note to update the tracking issue template!