`document.currentScript` works only while the script is initially
being processed. This means that when `publicPath()` was called from
a non-global scope, it failed to detect where ruffle.js is located,
which in turn failed to determine the .wasm location.
This simplifies the `publicPath` function and makes it useable inside
`fetchRuffle`.
Assuming `publicPaths` isn't used anywhere, this shouldn't be harmless.
relrelb