Add Windows (with WSL2) to GitHub Actions configuration

[AlekSi]

We should run at least some tests on Windows to ensure that the Windows+WSL2 development environment works.
(There are no plans to support developing on Windows without WSL2).

It should be possible to setup WSL2 on GitHub-hosted runners now:

• WSLv2 Support with updated Windows github-hosted runners actions/runner-images#10563
• https://github.com/vedantmgoyal9/setup-wsl2

[w84thesun]

I've tried to run tests on Windows Server runner.
There is 2 problems that makes adding tests on Windows hard:

1. To run all services that we need they should support Windows platform (neither PostgreSQL nor MongoDB does).
2. To run using WSL and linux containers there must be WSL2 support (it's not supported by github and we can't install it because it requires reboot of runner machine).

I suggest to add section to CONTRIBUTE.md with Windows development setup explained.