[Feature]: Option to enable and disable feeds

[martialblog]

Describe the feature request

We could provide a toggle for feeds so that uses can enable/disable them without deleting them.

[TheSyscall]

I'm not entirely sure that is necessary because there is no background update for the feeds.

The only thing that could change is the visibility in the combined feeds view.
And then it's more a show/hide then a disabled state.

[martialblog]

It's feedback I received from internal testers and a minor thing to implement.

I'm fine with calling it "show/hide"