Implement sounds with same volume level

All imported sounds (and videos) must have the same volume level to avoid too loud or quiet sounds in-game. Target volume is -6 dB

added Soundsystem basic label

set weight to 0

assigned to @pt033, @jg175, and @ms622

added Must Have label

changed the description

mentioned in commit b890e98a

removed Must Have label

added Nice to have label

closed