[TSD] Annotate comprehensive theming settings

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   1. Description

This PRs adds annotations for the comprehensive theme settings:

• `ENABLE_COMPREHENSIVE_THEMING`

• `DEFAULT_SITE_THEME`

• `COMPREHENSIVE_THEME_DIRS`

• `COMPREHENSIVE_THEME_LOCALE_PATHS`

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   1. Supporting information
      This PR part of the doc-a-thon effort.

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   1. Testing instructions
      N/A

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   1. Deadline
      None