Add an option to adjust the sound volume in the resulting video

[Calinou]

Is your feature request related to a problem? Please describe.
The sound coming from my video recordings is very quiet (almost inaudible at my default volume).

Describe the solution you'd like
Add an option to change the output video's audio volume, either as a percentage or as a gain in decibels.

Describe alternatives you've considered
I could increase my system audio volume, but I don't want to go deaf 🙂
My headset's volume slider has a minimum value that cannot be bypassed. It cannot be truly muted using the volume slider.

Additional context
N/A

[matanui159]

I have noticed that for some outputs (eg. my bluetooth earphones) the volume they are set to affects the volume recorded with ReplaySorcery. While other outputs (eg. my speakers) will record at 100% nomatter what volume they are set to. I think this is some bug in PulseAudio or the underlying infrastructure but have never gotten around to fixing it.