Create a js: URL Scheme

[jridgewell]

This is overflow question from the July 2019 meeting, particularly adressing @ljharb's importing concerns:

What if we created a js: URL scheme? We could then import builtin modules in two ways:

1. Import (sync or async) script

   <script src="js:temporal"></script>

2. Import module

   import Temporal from 'js:temporal';

When you import the script, you get some global added (eg, window.Temporal). This could be done sync (no attributes on the <script>), or async (<script async>).

When you import the module, you get the module.

[jhpratt]

How would this work for any standard library platforms (like Node or the web) might want to add on?

[jridgewell]

That's an entire other discussion we have to have. This is just an attempt to allow both script and module loading.