Adds Node-compatible protocolForURL
Adds Node-compatible protocolForURL

The current implementation of the DOM helper’s `protocolForURL` relies
on the implicit parsing and normalization that the browser’s DOM does
when setting the A element’s `href` property.

However, the DOM helper is often used with subset DOM implementations
like simple-dom. In those cases, we cannot rely on this normalization.

This commit detects when URL parsing doesn’t happen when setting the
`href` property on an `A` element and falls back to using Node’s
`URL` package.
tildeio/htmlbars,tildeio/htmlbars,mixonic/htmlbars,mixonic/htmlbars