Include all theme sidebars in REST API responses

[matt-bernhardt]

Developer

Stylesheets

• Any theme or plugin whose stylesheets have changed has had its version
  string incremented.

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• Relevant secrets have been updated in Github Actions
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Documentation

• Project documentation has been updated
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• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)

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Dependencies

YES | NO dependencies are updated

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  (not just this pull request message)
• The changes have been verified
• The documentation has been updated or is unnecessary
• New dependencies are appropriate or there were no changes

[matt-bernhardt]

Closing this without merging - this change is no longer needed, as the work to crawl the site efficiently has proven to be more achievable.