Asset Loading: Allow absolute paths

[bryphe]

Addresses an issue in #225 where absolute paths aren't loaded properly (we always prepend the working directory, today!)

TODO:

• Verify in WebGL strategy
• Update lockfile
• Clean up

[OhadRau]

Question: Would ~/x register as an absolute path in this case? I think it would be best if we could replicate the behavior of path resolution on the command line, so if that doesn't count as an absolute path we might want to look at a different approach.

[akinsho]

@bryphe @OhadRau maybe you could execute an echo command using Unix.open_process_in tested this out and the shell expands it. Other than a module that would do that for you the only way to get that kind of expansion is from calling out to a shell, I don't think its necessarily a blocker here but something that can be added on top or afterwards? 🤷‍♂️

[bryphe]

Superseded by #545