Chore: Allow extending the StudioCMSDashboard via the defineStudioCMSPlugin helper function

[Adammatthiesen]

Currently the defineStudioCMSPlugin allows you to configure front-end imports and tracking packages, this chore would also allow the plugins to create and add new pages into the StudioCMSDashboard

To do this we would have to add a new map that would resolve into This part of the routemap for the dashboard sidebar.

Also this would allow the completion of creating a full StudioCMS plugin, and it would then be possible to create full documentation on how to extend StudioCMS

[create-issue-branch]

Branch issue-0188 created for issue: Chore: Allow extending the StudioCMSDashboard via the defineStudioCMSPlugin helper function