Create a faster path to becoming a maintainer for un-maintained documentation guides

Problem/Motivation

There are a whole lot of un-maintained documentation guides right now. Which is resulting in a lot of content that is created, but never approved, as only a maintainer can approve and add content to the menu for a guide. For example, in #2860875: Permissions plan for Documentation Guide and Page content the Layout API guide was created and added to the D8 API's guide. However, that guide didn't have a maintainer at the time and so the new sub-guide was never approved. I was able to become the maintainer, but mostly only because I knew who to ask.

Right now you click the link to become a maintainer and it directs you to leave a comment on the guide asking for maintainership. The actual grant requires someone from the DA or others with sufficient admin permissions to notice the comment and grant the user the maintainer position for the guide. At the moment this seems like it might be creating a bit of a bottleneck. I'm not sure who is getting these notices, and/or how frequently they are being responded to. This guide for example has a waiting request https://www.drupal.org/node/2817929/discuss

Proposed resolution

One possible solution would be to allow someone to directly claim an un-maintained guide. Another option might be to provide better notifications to those who have the permission to grant maintainership.

Remaining tasks

TBD

User interface changes

TBD