CI: test dmd and ldc2 on ubuntu macos and windows

Signed-off-by: Andrei Horodniceanu <a.horodniceanu@proton.me>

.github/workflows/d.yml

@@ -15,12 +15,18 @@ permissions:
 
 jobs:
   build:
-
+    strategy:
-    runs-on: ubuntu-latest
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        dc: [dmd, ldc]
+    runs-on: ${{ matrix.os }}
 
     steps:
       - uses: actions/checkout@v4
       - uses: dlang-community/setup-dlang@v2
+        with:
+          compiler: ${{ matrix.dc }}
 
       - name: 'Build & Test'
         run: |