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...

- Migrated patches for 8.14.
- Up wacoq to 8.14 in docker image
- install: 8.14 requires `coq-core` and `coq-stdlib` to be installed.
- Set version 0.14.0.

Nothing too remarkable, code-wise, but a big change upstream is the
addition of `zarith` as a hard dependency.

TODO:

- update addons

Misc things that were out of date, and a new link to SF.

Closes #204

I have done a quick pass and tried to tidy the readme up a bit.

Please don't hesitate to further refine.

Closes #156.

Closes #154

Option values are `continue` and `restart`.

See #150.

Notes:

- added file with version, will be auto-generated in the future
- updated copyright headers in main file
- set release number to 0.11

`Ltac2` is pretty light (<=200Kb) and it doesn't depend on anything,
so it seems convenient for the user to have it around.

Changes in code are minimal. Additionally:

- we bump SerApi dep to 8.11
- implement a few primitive float functions so Coq's kernel doesn't
  complain on startup.

Build.md was renamed to build.md.
Fixes #130 .

Build.md was renamed to build.md.
Fixes #130 .

Possible settings are 'fixed' (the old behavior) and 'flex' (the new layout,
which is now the default).

Any other setting will make the layout not appear at all...

Addresses #91.

Using CodeMirror's dialog addon.
Also refactored the keyHandler in CoqManager.

We tag the version as 0.9.3 due to prior versioning by Shachar.

We do some cleanup in examples, addons, and miscellaneous bits.

All the changes were originally done in the Dune PR (#37), but as it
is delayed I've cherry-picked the bits that don't depend on the Dune
build itself.

Should mostly supersede #57.