Commonmarker 1.0 support

[ParadoxV5]

Description

• Add Commonmarker (all lower-case ms) provider for commonmarker ~> 1.0.0
  • Fixes #1528
• Remove tests for Markdown header IDs or the lack of, considering they may improve with newer provider versions and that YARD shouldn’t constraint their growth
• Also change “Missing markup renderer” from skip to raise to catch this sort of issues in the future

Completed Tasks

• [x] I have read the Contributing Guide.
• [x] The pull request is complete (implemented / written).
• [x] Git commits have been cleaned up (squash WIP / revert commits).
• [x] I wrote tests and ran bundle exec rake locally (if code is attached to PR).

[noraj]

I'm not sure if I understood all that was said here about the technical incompatibilities causes.

Why support several versions of commonmarker, why isn't yard supporting only the last version for each markup? Yes that's a potential breaking (of an optional feature, not of yard core), introducing new major version, and so what? People that want to keep older versions of the markup can still use older version of yard. Else, yard will still always be locked using outdated versions of markups. That would also be less cumbersome and maintenance work than having a system for version requirements and maintaining several plugins for each major version of each markup. If only one version of commonmarker should be supported, it should be the latest.