feat(docker): add dockerfile

[javigomezo]

Hi @remvze, love your project!

Small PR for adding the dockerfile (solving #1). It's my first time creating a Dockerfile for Astro, I followed the official docs and I think it's working.

Of course for building just

docker build -t moodist .

And for running it:

docker run -it --name moodist -p 4321:8080 moodist

[remvze]

Thank you for your contribution!