Revamp the docker image for the front-end

[dannywillems]

• Add Sentry in the docker-compose
  • Follow-up on Node dashboard: setup sentry #1483
• Support sentry in the docker image
  • Follow-up on Node dashboard: setup sentry #1483
• Support the following environment when running the frontend:
  • webnode
  • frontend
• remove gtag as specific to openmina.com, and we remove references to OpenMina
  • frontend: remove gtag as unused now #1456
• add a section on the website to:
  • replace frontend/README.md
  • build the docker image for the frontend
• update the environments if necessary with new nodes:
  • src/app/assets/environments/staging.js stills uses old nodes.
• rename openmina.scss into mina-rust.scss and update all references to openmina.scss.
• frontend: rename openmina.scss to mina-rust.scss #1467
• setup prettier - see Frontend: set standard for code formatting with prettier #1457
• use a Makefile for each available target in package.json.
• have a Makefile target for each build configuration for the frontend (note that ng build --configuration [CONFIG] is a built-in from Angular CLI).