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).