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

Please don't hesitate to further refine.

[build] Pin to Coq 8.11.1

[build] Always rebuild coq-pkgs

This is a workaround for #171 until we have something better.

`make coq-get-latest` will get the tip of the branch.

Still it is fairly useful to deliver jsCoq with additional patches so
we don't have to wait for official releases.

Thanks to Shachar for the careful review.

Native (.cmxs) plugin is needed for compilation.

[addons] Add QuickChick

[build] Fix missing dependency on addons install directory.

Since a few versions Chrome is not running well with local files,
returning a HTTP status of 0; we could fix that in the OCaml code but
actually using a real server seems like a good idea.

Closes #137

Fixes #171

To alleviate vulnerability in minimist.

Now needed due to changes upstream.

 Freshen up the look of the landing page.

[contributing] Some notes about review / merge

For a while I've been wanting to make clear that the development here
should not turn into something too bureaucratic and we should not be
afraid at all of committing stuff to master. I guess just before the
move to an organization this update should happen.

I dunno about the wording tho, suggestions welcome.

Startup error caused from absence of lookbehind patterns (an ES2018 feature).

Fix project-builder

Adjust for changes in PackageManager.

Allows for simpler config options when specifying multiple package directories.

(This bug is fixed upstream.)