CI: run on windows

Don't know if it works, let's try :-)

'windows-latest` currently means Windows Server 2022
(https://github.blog/changelog/2022-01-11-github-actions-jobs-running-on-windows-latest-are-now-running-on-windows-server-2022/)

.github/workflows/actions.yml

@@ -14,16 +14,24 @@ jobs:
     runs-on: ${{ matrix.os_and_command.os }}
     strategy:
       matrix:
-        ruby: [ '2.5', '2.6', '2.7', '3.0', '3.1', 'ruby-head', 'truffleruby-head' ]
+        ruby: [ '2.5', '2.6', '2.7', '3.0', '3.1', 'ruby-head' ]
+        # The k0s script does more testing but needs docker, only works on ubuntu.
         os_and_command:
-        - os: 'macos-latest'
+        - os: macos-latest
+          command: 'env TESTOPTS="--verbose" bundle exec rake test'
+        - os: windows-latest
           command: 'env TESTOPTS="--verbose" bundle exec rake test'
         - os: ubuntu-latest
           # Sometimes minitest starts and then just hangs printing nothing.
           # Github by default kills after 6hours(!). Hopefully SIGTERM may let it print some details?
           command: 'timeout --signal=TERM 3m env TESTOPTS="--verbose" test/config/update_certs_k0s.rb'
         include:
-        # run rubocop against lowest supported ruby
+        # As of 2022 Aug, truffleruby-dev-builder had no build for windows.
+        - os: macos-latest
+          ruby: 'truffleruby-head'
+        - os: ubuntu-latest
+          ruby: 'truffleruby-head'
+        # Run rubocop in 1 job only, against lowest supported ruby.
         - os: ubuntu-latest
           ruby: '2.5'
           command: 'bundle exec rake rubocop'