wip vanilla entrykit

[frolic]

borrowed from our old friend https://github.com/latticexyz/mud/pull/2623

I don't think we need to do a vite build this time because we're still expecting these to be imported/bundled downstream by something like vite in user land. (Whereas before we were trying to create a JS bundle that could be imported via a <script> tag.)

[changeset-bot[bot]]

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