Dockerfile and scripts for development

[schnittchen]

Hi there,

I wanted to see if I can work on tiddlypouch locally, so I set up a docker container with all the software needed for building and running it. I assume you are not using Docker for working on tiddlypouch, and that's totally fine with me.

The changes in this PR could make it easier for people to contribute in the future, even if they don't use Docker, because by looking at the Dockerfile they learn to some degree what they need to install (*). For contributers willing to work with Docker, this should make things significantly simpler. In general, using Docker in this way helps keep the host system clean from a particular project's requirements (with the exception of Docker, of course), which is really helpful when projects require conflicting versions of, say, nodejs.

(*) because I was lazy and installed a "meta package", this is not as detailed as it could be

There's a few things that aren't solved so far:

• The setup assumes the developer works as the unix user with uid 1000 outside of the container. Obviously not ideal, but fixable
• I needed to add two add two scripts in package.json to get the server to bind to 0.0.0.0, otherwise exposing the server to outside the Docker container does not work. I kept the existing scripts as they are.
• Not everything is set up for every situation -- testing requires a browser installed, and I did not bother with that yet

Before putting any more work into this, I would kindly ask if this setup, after being brought into a good shape, is a welcome contribution to the project.

One obvious risk of adding this is the added maintainence burden, in particular if the core developers do not use Docker.

[schnittchen]

Got integration tests running, ran yarn run nodemon ./node_modules/tiddlywiki/tiddlywiki.js ./wiki --build (is this the right way?) to populate ./output. The png diff indicates that installing some fonts might get that test green too...