0.5.2 release

• added imga and vida for loading images and videos with access to alpha/transparency channel
• added gdm and gdma for access to window/display capture (via browser's getDisplayMedia pathway)
• added cama as an RGBA variant of cam (RGB) that is transparent outside of the unit square
• fixed a bug in which video textures would interfere with simultaneous image textures
• all image textures (img,img,vid,vida,cam,cama,gdm,gdma) are implicitly 'fit' to aspect ratio (based on their resolution in pixels)