Cell state manager

[coatless]

In this PR, we introduce a cell state manager that:

1. Stores each cell and code inside of JS; and,
2. Allows for consistent execution of output and setup code cells with values in packages.

Implementation status: In progress

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Q: Why are there so many instances of globalThis.* =?

A: We're trying to avoid needing to register standalone HTML dependencies like a JavaScript file. Thus, we have multiple "module" files setup in <script type="module"> JS HERE </script>.

If we registered a JS file, this would require us to be able to have the JS persist to the publish phase. In this case, we could then do:

<script
  src="./qwebr-module.js"
  type="module"
></script>

<script type="module">
  import { initWebR } from "./qwebr-module.js";
  ...
</script>

---

Once resolved, this should address:

Close #114, Close #105, Close #88