Convert to a Silverstripe site (before 6 stable, maybe before 6 beta)

[emteknetnz]

We decided to not migrate to github pages for the following reason

api.silverstripe.org should be converted to be a Silverstripe so that it is easier to maintain. Notably, it need to use Queuedjobs to handle cron operations

Notes

• doctum currently uses htdocs/ as its build dir where all the static files live. This will need to be swapped to the public/ dir.
  • Make sure when the docs are written, nothing else in public/ is affected

Acceptance Criteria

• The same favicon dev docs uses is included
• Only the modules which are required are installed
• Queued jobs is set up to run on a cron via .platform.yml
• A queued job is added as a default job
• The cleanup job is added as a default job to ensure completed jobs are removed from the queue
• The queued job runs every day
• All of the static content continues to work as expected
• The /search/lookup route continues to work as expected (this is what the docs site uses for API links)
• Appropriate .htaccess rules are retained
• The default version is still 5 and is still easy to change
• The CMS 6 docs are included in the site