add arrow key support to block container scrolling
add arrow key support to block container scrolling

pikurasa/musicblocks,Kachachan/musicblocks,sneh1234/musicblocks,tradzik/musicblocks,tradzik/musicblocks,hemantkasat/musicblocks,sneh1234/musicblocks,sneh1234/musicblocks,Kachachan/musicblocks,pikurasa/musicblocks,hemantkasat/musicblocks,pikurasa/musicblocks,Kachachan/musicblocks,hemantkasat/musicblocks,tradzik/musicblocks