Consolidate project maintainer articles

[lelia]

Proposal

Currently, the site has several articles on maintaining projects, establishing project maintainership, and project dependency maintenance. We should collapse these under a single 'Maintaining Projects' (or similar) parent page for better discoverability.

We should also be sure to update any relative cross-links in other articles to reflect the new url path(s).

Affected pages

• Maintaining a Project
• Managing Project Dependencies
• Project Maintainership

Proposed parent page

• Maintaining Projects

Proposed sub-pages

• Maintaining Open Source Projects
• Managing Project Dependencies
• States of Project Maintainership

[GaryPWhite]

makes sense to me.