added Dockerfile to run a simple docker container with a webserver

[kubax]

This PR adds a (very) simple Dockerfile to compile inside a Docker Container and also start a simple webserver to test or use the calculator.

Inside the Dockerfile i include the PR from zuils10 to be compatible with the unity savegames.

[tomcur]

Thank you!

It would be especially useful to add another script that runs the build using Docker and copies the generated build from the container to the host. So there would be two Docker scripts: one for running a server for testing, and one for producing a production build.

[tomcur]

Note the build tool was changed from NPM to Yarn.

[kubax]

updated and added a script to copy the files.

to Build the image call:

docker build . -t clickerheroescalculator

then either run it with:

docker run -p 8080:8080 clickerheroescalculator

or copy the files with:

./copy-dist-from-docker.sh