Support line numbers in file paths

[PsychoLlama]

I haven't implemented mappings that check for line numbers after the file path simply because it's not a common pattern in JavaScript. Recently I noticed someone using further with ag output, which looks a bit like this:

src/utils/prefetch.js:5: * @return {Promise<void>} - Resolves after successfully caching.
src/resolvers/scene.js:2:import resolveLight from './light';
src/resolvers/scene.js:26:    return this._lights.map(id => resolveLight({ id }, context, info));

That's ideal output for gF and <c-w>gF and a really good excuse to write more vimscript.