Add option to not lower volume on window becoming inactive

[jai-x]

Would be nice to have the option for the game volume not to lower when becoming inactive.

I realise this is probably heavily linked to the discussion in #13173 W.R.T having more setting toggles which is not desirable but I figure the use case and UX argument is completely different so it was worth opening a discussion.

[Susko3]

Just set this to 100%.