Docker support

[alkimake]

• docker build
• docker run

Usage:

$ docker build -t pairist_v2:latest .

$ docker run -e PAIRIST_FIREBASE_PROJECT_ID=<firebase_project_id> -e PAIRIST_FIREBASE_API_KEY=<firebase_project_api_key> -e FIREBASE_TOKEN=<firebase_token> -p 8080:80 pairist_v2:latest

[alkimake]

Converted into draft pull request since I couldn't make it working with following error I get.