add a Dockerfile

[marten-seemann]

This makes it easy to run qvis locally when the hosted qvis happens to be offline.

You could also consider publishing a Docker image on Dockerhub / on the GitHub Docker registry. Should be pretty straightforward to publish a build for every push to master. Let me know if you'd be interested in a follow-up PR.

docker build . -t qvis
docker run -p 8080:8080 qvis

[rmarx]

Thanks Marten.

I do have a docker setup for qvis, but it's in this separate repo, as it also contains ways to setup the server-side things needed for loading pcaps / bypassing CORS stuff. If you're just running the frontend it's indeed pretty straightforward.

I'll keep this PR in mind for the new version for people that indeed just want a quick way to run the frontend.

[marten-seemann]

This PR was not intended to replace your current setup, but just as a way to easily run qvis locally. Any reason to not just merge it?