We have been vendoring noVNC to get vnc_lite.html,
maintaining a patch file so we could upgrade the version of
noVNC used if needed.

noVNC publishes a JS library [on
npm](https://www.npmjs.com/package/@novnc/novnc)
that we can easily use instead, and stop vendoring the whole
package! This brings us the following massive advantages:

1. No more vendoring an entire package in!
2. Upgrades of noVNC client become practically trivial
3. We can change the frontend as we wish much more easily,
   compared to having to maintain a patch file as we do now.
   PRs like
   #7
   become easier.

This PR:

- Adds a `package.json` to include the noVNC js package
- Adds a `webpack.config.js` to provide JS bundling, so we can just ship
  a single `viewer.js` file that has everything.
- Adds appropriate bits (stolen and adapted from jupyterhub's config)
  to package the built JS in the final wheel as necessary.
- Upgrade from noVNC 1.2 to 1.4, but otherwise keep everything the
  same. I just copied our patched `vnc_lite.html` into `index.html`,
  and just split out the JS / CSS.
- prettier with pre-commit has done its thing on the JS, CSS and
  HTML. This is fine, as I am hoping we can make more changes to the
  UI after this.
- Modify the `Dockerfile` to setup the conda env first, and then
  separately install the python package with pip. This makes local
  development *much* faster.
- Add a `.gitignore` (which this repo was missing), with
  node_modules included as well as the dist/ directory with the built
  JS.

This allows for much faster iteration, by simply mounting
$(pwd) into /opt/install