Adding more options for volume

[AlmasB]

Discussed in #1180

^{Originally posted by nicymike June 10, 2022}
Hey!

1. What do you think about adding a new setting to audio for master volume.
   Many games have three (or sometimes more) volume sliders: master, music, sound.
   The volume for playing audio is then calculated by:
   soundVolumeForPlay = master * sound
   musicVolumeForPlay = master * music

2. What do you think about adding the possibility to play a sound with a different volume eg. adding a new optional parameter to the methods for playing a sound or music.
   In my game I have certain sounds for ambience which should be played with lower volume.
   What I am currently doing with FXGL is: 1. Lower sound volume, 2. Play sound, 3. Raise sound volume.

[AlmasB]

Relevant extract:

That's a good point. It seems the implementation is hidden from public API. This might have been necessary to hide cross-platform support (particularly on mobile), but I don't see why we couldn't open access to getAudio(). From the list you will note the method is actually there, just hidden in $fxgl_core. I'm happy to turn this into an issue, so we can track it and fix it eventually.