Add support for Github Actions build number #847
Description
Describe the idea (required)
Currently there is no support for build number in Github Actions integration. Maybe it was not that straightforward at a time when the plugin was created.
Now it seems quite trivial, we simply have to take value from GITHUB_RUN_NUMBER environment variable.
See https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/store-information-in-variables.
Tell us about the expected behaviour (required)
It is expected to get build.number variable in the plugin populated.