Fix module branches and tags

Problem/Motivation

This module has broken away from recommended branch and release tagging.

It presently has these branches, and corresponding recent tagged releases:

• 7.x-1.x (not relevant)
• 8.x-1.x; 8.x-1.0-rc5, 8.x-1.0; all good
• 8.x-2.0; this should not be a branch, delete it if possible. It is branched off at 8.x-1.0 tag.
• 8.x-2.x; 8.x-2.0 (tag), 8.x-3.0; these tags do not follow semantic versioning, @see Transitioning from 8.x-* to semantic versioning →

The 8.x-2.x branch should have been called 2.x or 2.0.x, and be tagged as 2.0.0 for release.

The 8.x-3.0 tag should have been on 3.x or 3.0.x branch, and be tagged as 3.0.0 for release.

Proposed resolution

• Make a new branch on the next available release numbering, which would be 4.x or 4.0.x. Neither branches starting with 2.x or 3.x can be used as they lined up with the 8.x-2.x and 8.x-3.x
• Make a tagged release on this branch of 4.0.0.
• Make a dev release for 4.x-dev or 4.0.x-dev
• Set the new default branch to be 4.x (or 4.0.x) @see Setting a default branch →
• Delete the 8.x-2.0 branch if possible. Or ask the Drupal Infrastructure people to remove it for you.
• Please review: https://www.drupal.org/docs/develop/managing-a-drupalorg-theme-module-or... →

Remaining tasks

• ➖ Create 4.0.x branch from current HEAD
• ➖ Set 4.0.x as default branch
• ➖ Tag 4.0.0 release and publish it
• ➖ Make a development release so that pipelines work and show on project page
• ➖ Delete the 8.x-2.0 branch, or ask DI to do it if the interface does not allow it