Allow for long running tasks

[Freyja-moth]

When working on a bevy game someone may want to have multiple long running tasks on in the background, such as a server, tests that watch for changes and so on.

It'd be useful to have a section in the editor dedicated to this, something similar to mprocs perhaps.

[jbuehler23]

I think this would be useful to have - but might be more for something after we have a working read-only editor. Thoughts @alice-i-cecile ?

[alice-i-cecile]

Yeah, this is not directly on the critical path :)