added more commented notes to music.xml and sounds.xml for modders

added more commented notes to main.lua and music.xml for modders

added placeholder code for new tracks in music.xml

just added a couple more helpful notes to the comments of the music.xml

-fixed the downpour and dross mirror world tracks being labelled as 'ascent' and using 'bad seeds' instead of 'arboretum'
-changed hush phase 1 music
-changed boss rush complete jingle

updated music.xml to have a set main menu track and added in a couple missing example entries for reference

added repentance tracks

sfx jingles update

set missing challenge start sound

raised volume of sound that was bit quiet
cropped 10 seconds of silence from start of one of the songs