Add UMD builds backs in the core

[Andarist]

I'm not a fan of shipping those in 2022 but this has been asked on Discord. I don't want to work too much on those bundles because I think that if somebody needs those then they need to figure out creating those on their end (it's not that hard and we won't have a lot of consumers for those bundles nowadays).

The main problem with them for us is that Rollup doesn't support code-splitting for such targets:

Error: Invalid value "umd" for option "output.format" - UMD and IIFE output formats are not supported for code-splitting builds.

This can easily be checked on their playground

So since code-splitting isnt' supported we have to bundle all of the entrypoints separately and that might cause issues with shared state, instanceof and similar.

Alternatively we could prepare special "all at once" UMD bundles but... that would complicate our setup and would have rather poor RoI given how niche those bundles are nowadays.

I'm kinda providing those here with a disclaimer that YMMV. I didn't test them in full and stuff might not work properly.

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🦋 Changeset detected

Latest commit: 8da759c

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xstate	Patch

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[Andarist]

We've missed this in #3187

[Andarist]

I'm leaning toward reverting this. UMDs are a weird beast of the past. In today's landscape, you can either use a bundler-powered CDN like Skypack or you can find the ESM files in our packages that are compatible with browsers.