Post-docsy conversion

[chalin]

Followup to #134. Alternative tracker for the post-docsy milestone.

• Clean out any unused assets, layouts, etc from the pre-docsy version of the site
  • Delete unused nav-panel.html Delete unused nav-panel.html #281 -- handled this file separately in support of Config: cleanup and rename default branch to main #282 and Rename master branch to main #149
  • Package.json cleanup: remove unused bulma et al Package.json cleanup: remove unused bulma et al #292
  • Check if we still need specific files after initial docsy-conversion:
    • Check for obsolete files after initial docsy-conversion #139
    • Pruning unneeded static/apispec/swagger and css partial #388
• Versions menu UX issue Versions menu UX issue #304
• Doc-version landing pages:
  • Consider reintroducing page descriptions on version landing pages as part of IA discussion Adding annotations to v3.5 Table of Contents page #386
  • Doc-version landing pages need rework Doc-version landing pages need rework #300
• Automatic page generation is preserved (see Ensure that generated documentation gets merged into website automatically (etcd-io/website) #111 & Ensure that generated documentation gets merged into website automatically etcd#12768)
• Ensure that the branch name in the config file is switched back to master (Fix github links on docs pages #246, updating config.toml #248)
• (Minor) Fix broken internal links: latest Drop About from docsy MVP, and make link checker happy #227
• List of generated metrics files (as per conversation Move historic metrics files #171 (comment)) Reinstate metrics #242
• Setup Blog URL Permalinks Setup Blog URL Permalinks #140
• Re-enable analytics - Reenable analytics #249
• Footer: copyright date range should match license file Updating footer copyright date to match LICENSE #258
• Correct UI feedback links Correct UI Feedback links in config file #256
• Ensure that author names appear in blog entries Updating author frontmatter format #259
• Address Hugo warning: Page.Dir is deprecated and will be removed in a future release. Use .File.Dir Eliminate Hugo warning about .Page.Dir #263
• Homepage CTA buttons: replace GH by Learn more Homepage CTA buttons: replace GH by Learn more #305