[Feature Request] Disable Migration/Search Sources

[Patricol]

What feature should be added to Suwayomi?

Allow toggling whether or not each Source is used in Global Search and/or Migrations.

This could be a setting in the Source tab of the Browse section; or perhaps appear everywhere the Allowed Languages setting shows up; because it serves a similar purpose.

Why/Project's Benefit/Existing Problem

The most obvious use-case is to avoid querying sources that only provide a single item, e.g. webcomic sources like xkcd.
Even if those searches are stubbed out in code; they still clutter the UI for Global Search and Migration.

I think people will find other uses for this feature though; like temporarily disabling sources they don't intend to use during a manual bulk migration.