apps: designate compiled js/css files as binary
apps: designate compiled js/css files as binary

The 'index.js', 'tile.js', and 'index.css' files included in several
Arvo apps are compiled, minified JS or CSS.  While they are technically
text, they are not usefully diffable.

This commit designates such files as 'binary' in .gitattributes, which
prevents git from attempting to create diffs for them in 'git log' and
'git show'.

jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit