`<kbd>` formatting and a hint for newcomers to look at the scratchpad icon.

Also generated symbols for the examples.

It is no longer in use. Serving from source dir still works with `make links`,
but you must run `make links-clean` before building with Dune again.

This fell into disrepair following some refactoring of the package format.

Updated to reflect current implementation.
Fixes #267.

Filled in the links in the navbar, etc.
Added hover action to quick-start reference.

Added meaningful names to comparison lemmas.
Renamed module to `sqrt_2` so the import looks nicer on the landing page.

Added flag `--no-recurse` to disable subdir recursion when building
packages.

Added a link to Coq in "settings".
The top-left link now points to jsCoq's homepage instead.
Landing-page CSS moved to a separate file.

As suggested by @hannelita.

It is longer, yes, but perhaps easier to understand in prose.
Fixed indentation.

Allows multiple jobs to invoke the SDK in parallel. If the SDK is not installed,
the first to lock the file will carry out the install.

A bind-mount is too slow.
`sudo` is required to copy onto the volume.
The implementation is currently non-reentrant, so `-j1` is needed.

Allow specifying sub-branch for quick testing of feature branches.
Makefile targets for uploading SDK images to Dockerhub.

This directory is now excluded from Dune. Because it contains `dune`
files that serve as examples themselves.
(Currently, there is one in `sdk-demo`.)

When mounting `/home`, gosu may inadvertantly write to the host's
because of `useradd`.

As subcommand `jscoq sdk`.

Allows a dev to only build core jsCoq and SDK.

Included `index.html` and a `package.json` to show how to load
and run the resulting package.

Also added `playful.html`. (Which is a bit unrelated.)

Currently separate from the main cli, but for no good reason.
Should be a sub-command.

Made the example a little bit smaller by removing some unneeded
boilerplate.
(Possible thanks to Dune 3's `glob_files_rec`.)

Also, the example now showcases `group-theory` instead of Coqoban.
Mainly because we already have Coqoban as an addon.

Docker multiarch

We will keep editing to add some documentation around the actual proof.

Cleanup apt lists.