Add option always include broadcaster in user completions

[KleberPF]

Settings text probably needs to be improved.

Setting off:

Setting on:

I noticed we got some unit tests for ChatterSet, so let me know if I should add any.

Fixes: #5190

[Nerixyz]

Looks good! Maybe the setting name could be a bit shorter with some tooltip text, but I can't think of anything good right now 🙃

If you want, you could add a test case (maybe testing the case-sensitivity).

[pajlada]

The "at the top" isn't important to me, just that the streamer is included. So for the variable names & the setting labels that should be reflected (e.g. "always include broadcaster in user completions" or something)

[KleberPF]

Changed the setting name (might be too big now but I feel like it's reads well)

[KleberPF]

@pajlada ended up using find_if, erase and insert, everything seems to be working. It doesn't seem too hard to add InputCompletion unit tests, just mock accessChatters and create a ChatterSet using preset names, but I'm a Visual Studio guy and CMake is kicking my ass. I wasn't able to figure out how to compile the tests, so if you could give me some pointers on how to do that I'd appreciate it a lot (of course, feel free to add the tests yourself if you want)