[REQUEST] Ability to set primary merge

[XenitXTD]

Description A clear description of the feature

Ability to set primary merge

How would it improve the App? How would the feature improve the app?

This would allow you to unmerge the source that you originally started with as well as several other things described in additional context

Additional context Add any other context or screenshots about the feature request here.

So the merge functionality is genius but there have been cases where trying to use the default source mangadex as primary and merging all to that but many times other sources have more up to date info so you want to switch primary

If you unmerge primary it just removes all merge links and keeps primary bookmarked

There are other benefits to being able to select primary for example you and use that to track chapters notify for updates only from primary source and also if implementing an auto download chapters it tracks primary source so while you have merged all that tracks on primary source and puts it in the hands of the user to manage and decide what source is primary while still making visible other sources and their latest chapters

It also means a change or removing a merge becomes a case of changing primary to another source and unmerging old primary source