Build all environment in CI

[guyou]

Since the firmware can be used on many environments, it could be useful to have CI to check that all of these are building fine.

I did two experiments around this:

• building all env in one Job (took around 30 min):
  • result: https://github.com/guyou/My-TTGO-Watch/actions/runs/1921918021
  • code: https://github.com/guyou/My-TTGO-Watch/blob/ci-build-all-env/.github/workflows/main.yml
• using a matrix build (took 7 min and used 10 workers):
  • result: https://github.com/guyou/My-TTGO-Watch/actions/runs/1922979010
  • code: https://github.com/guyou/My-TTGO-Watch/blob/ci-build-all-env-matrix/.github/workflows/main.yml

Let me know what solution have your preference and I will create a pull-request.

[sharandac]

Thank you for your suggestion. I have tried the second variant and inserted it into the experimental branch.