Update dockerfile and env variables

[krumware]

Testers needed!

This PR updates the dockerfile and should run properly with a static site configuration (running yarn start instead of the yarn dev workaround)

Create a .env file by copying and renaming .env.example then substituting your variables. BASE_URL and NEXT_PUBLIC_APP_URL need to be set at build time. Use docker-compose build to accept those env variables automatically, or pass in the env variables manually using docker build args.

API-related variables (like the google API key) should work at runtime.

closes #50
closes #46
closes #45
related to #43

Note: additional customization and dev experience features are expected for the future. this intentionally takes a small step forward

[JanBobolz]

Definitely compiles and works now. Got it running on localhost and on the web. Thanks for the great work!

I have a few notes in my review.

Google calendar and zoom integrations work.

[wivaku]

What should I do to test? Should I use the regular git clone --recursive https://github.com/calendso/docker.git calendso-docker?

With that still getting the "accept our license banner" and no integrations, and when changing the script to yarn dev the app fails to start, with message in the log:

calendso         | Error: > Couldn't find a `pages` directory. Please create one under the project root