test for compile errors on build server

See [WIP](https://github.com/Task-Tracker-Systems/Task-Tracker-Device/blob/b15d1c66f6a9f15ea43c1113b92add38f36187d3/.github/workflows/platformio.yml#L29).

Acceptance criteria:

- build server automatically builds and reports compiler errors
- compiler errors inhibit merging a pull request