Migrate engine & modules to jsr

[NathanFlurry]

Motivation

This is the new standard by Deno.

The old HTTPS-based modules is way simpler to manage from our end, but deno.land & esm.sh are deprecated.

Need to look at the industry to see who's supporting JSR.

Implementation

TBD on if the engine should use import maps or stick with the old deps.ts. This might complicate the installer script if we use import maps.

TBD on if modules should use import maps, probably not. This complicates things way too much.