Add build and release workflow

[joschi]

This PR adds a GitHub workflow which builds co2monitor on ARMv7 (Linux), AArch64 (Linux), and AMD64 (Linux and macOS).

If the build was triggered by pushing a tag, it will interpret the tag as version, create a GitHub release, and attach/upload the build artifacts to it.

For building the ARM-based versions of co2monitor, we're using QEMU to emulate the respective machine architecture, since the Rust cross-compiling chain doesn't quite work because of the dependencies to native libraries (libusb, libudev, libhidapi).

Examples:

• Non-release run: https://github.com/joschi/co2monitor/actions/runs/166507659
• Release run: https://github.com/joschi/co2monitor/actions/runs/166508190
  • Created GitHub Release: https://github.com/joschi/co2monitor/releases/tag/v0.1.0

[joschi]

@gtudan And of course thank you very much for building co2monitor! It's humming along nicely in my office to monitor the air quality. 😄