We reorganize jsCoq's source code as to be more modular, in particular
we start to place backend files under the `backend` directoy, and
frontend files under `frontend`.

Code as it now does work, note however that still quite a bit of work
is needed. In particular, the headless frontend should get its own
directory, the coq-jslib directory should go away, use more types,
etc...

Newer webpack{,-cli} support this.

In princple, should change Ronin to not rely on the literal name
of the constructor.

When content-length is not available (Vercel T.T).

In `type="module"`, this has to be done explicitly.

This is not best.

The bundle (`.bundle.min.js`) is now needed for the menu.

Changed codename, seems more temporally fitting.

Quick help

Need to pass `backend` and `is_npm` properly now.

Need to pass `backend` and `is_npm` properly now.

This is just the actions table from the landing page, with
appropriate formatting borrowed.

(The panel is empty of yet.)

The monkey-patched Array methods are up for removal.

Disabled `strictNullCheck`, because it's too hard to
satisfy at the moment.

[misc] Misc fixes to playful and the test runner.

[js] Enable ts-check type checking + some annotations

Still, both don't fully work, needs more research as to witness what's
broken.

Not sure if this is very useful, but trying out.

[js] [refactor] Remove use of JsCoq global in components.

Instead of using a JsCoq global, we pass the needed parameters to the
constructors so the components types are more functional.

The access to the global was mostly used to determine the backend, but
IMHO this is morally wrong as nothing should preclude a manager
creating N worker objects with different backends.

Moreover, most of the backend case analysis should go away once we
improve backend handling.

This is also a step towards frontend / backend separation.

Next step is indeed to isolate the backend options in their own
interface.