Install mono on macos gh-actions machines

Author: eiriktsarpalis

.github/workflows/ci-build-test.yml

@@ -50,6 +50,10 @@ jobs:
       if: runner.os == 'Linux'
       run: sudo apt-get install -y mono-devel
 
+    - name: Setup Mono on macOS
+      if: runner.os == 'macOS'
+      run: brew install mono
+
     - name: Set up Node.js
       uses: actions/setup-node@cdca7365b2dadb8aad0a33bc7601856ffabcc48e # v4.3.0
       with: