feat: Provide an easily reusable Web SDK

[dcodeIO]

Using the AssemblyScript compiler on the Web currently requires multiple steps to make it work, which includes manually updating the import map on version bumps and optionally providing a shim for import maps. Instead of providing a workaround by exposing the import map in a script plus longish instructions, this PR changes the mechanism to a single script that sets everything up.

Usage is

<script src="https://cdn.jsdelivr.net/npm/assemblyscript@latest/dist/web.js"></script>
<script type="module">
import asc from "assemblyscript/asc";
...
</script>

where latest can be any version since the change, and additional query parameters can be used to modify behavior:

• web.js?noinstall does not install the import map
• web.js?noshim does not install the import map shim
• Both can be combined with a ,

Regardless of the parameters used, the following global variables are always available:

• ASSEMBLYSCRIPT_VERSION containing the current compiler version
• ASSEMBLYSCRIPT_IMPORTMAP containing the import map, which includes all relevant versions in the URLs

Removes the web.html and importmap.js artifacts, with importmap.json (for documentation) and web.js remaining. Reverts e1a5fce.

• I've read the contributing guidelines
• I've added my name and email to the NOTICE file

[CountBleck]

I think you should use # instead of ? so different options don't get cached separately.

Edit: never mind, the entire URL is checked, so either works.

[dcodeIO]

Yep, we could document either. Not sure about the effects in practice, though, as I think caching is per origin nowadays anyway. Could be useful if the same origin uses multiple configurations, though.