update readme.txt windows build instructions
update readme.txt windows build instructions

ucdseniordesign/avian,badlogic/avian,bgould/avian,minor-jason/avian,bgould/avian,bigfatbrowncat/avian-pack.avian,bgould/avian,dicej/avian,joshuawarner32/avian,lwahlmeier/avian,marcinolawski/avian,dicej/avian,badlogic/avian,getlantern/avian,badlogic/avian,badlogic/avian,lwahlmeier/avian,minor-jason/avian,marcinolawski/avian,MaartenR/avian,dicej/avian,dicej/avian,getlantern/avian,ucdseniordesign/avian,lwahlmeier/avian,joshuawarner32/avian,marcinolawski/avian,lostdj/avian,MaartenR/avian,bigfatbrowncat/avian-pack.avian,lostdj/avian,marcinolawski/avian,ucdseniordesign/avian,bgould/avian,getlantern/avian,lostdj/avian,minor-jason/avian,ucdseniordesign/avian,lostdj/avian,getlantern/avian,bigfatbrowncat/avian-pack.avian,MaartenR/avian,minor-jason/avian,bigfatbrowncat/avian-pack.avian,joshuawarner32/avian,MaartenR/avian,joshuawarner32/avian,lwahlmeier/avian