allow "code splitting"

[jaeh]

some libraries will be big.
three.js, web3 etc.

they might also be set by a extension (window.web3 for metamask iirc)

todo: build functionality to check if window[varname] is set,
if it is not, add a script to the html page that exposes window[varname],
wait or load, then do whatever the page needs.

all of that with a nice loading anim pls.