message: Add S-inactive-closed documentation.
diff: @@ -13,12 +13,14 @@ Status tag meanings:
  - [S-waiting-on-team] - A T- label is marked, and team has been cc-ed for feedback.
  - [S-waiting-on-bors] - Currently approved, waiting to merge.
  - [S-waiting-on-crater] - Waiting to see what the impact the PR will have on the ecosystem
  + - [S-inactive-closed] - Closed due to inactivity.
  [S-waiting-on-review]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+sort%3Aupdated-asc+label%3AS-waiting-on-review
  [S-waiting-on-author]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+sort%3Aupdated-asc+label%3AS-waiting-on-author
  [S-waiting-on-team]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+label%3AS-waiting-on-team+sort%3Aupdated-desc
  [S-waiting-on-bors]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+label%3AS-waiting-on-bors+sort%3Aupdated-asc
  [S-waiting-on-crater]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+label%3AS-waiting-on-crater+sort%3Aupdated-asc
  +[S-inactive-closed]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+label%3AS-inactive-closed+sort%3Aupdated-asc
  # Procedure:
  @@ -53,7 +55,7 @@ update, ping the author on GitHub asking for an update.
  If the author's been unresponsive for more than 14 days, close the PR due to inactivity and ask the
  author to reopen when they have a chance to make the necessary changes. Make sure to thank the
  -author for the changes.
  +author for the changes. Also tag the PR with S-inactive-closed.
  [S-waiting-on-author PRs]: https://github.com/rust-lang/rust/pulls?q=is%3Aopen+is%3Apr+sort%3Aupdated-asc+label%3AS-waiting-on-author
  @@ -120,6 +122,13 @@ acrichto, brson, tomprince, and frewsxcv and request a crater run.
  [S-waiting-on-crater PRs]: https://github.com/rust-lang/rust/pulls?utf8=%E2%9C%93&q=is%3Aopen%20is%3Apr%20sort%3Aupdated-asc%20label%3AS-waiting-on-crater
  +## [S-inactive-closed PRs]
  +
  +These never need to be looked at. PRs which have been closed due inactivity. This is a terminal
  +state for the time being, primarily oriented towards easing future work.
  +
  +[S-inactive-closed PRs]: https://github.com/rust-lang/rust/pulls?utf8=%E2%9C%93&q=is%3Aopen%20is%3Apr%20sort%3Aupdated-asc%20label%3AS-inactive-closed
  +
  ## Updating the Spreadsheet
  Finally, once all steps are complete, go back through and get counts for each PR status tag. Log
  