Update d.yml

.github/workflows/d.yml

@@ -63,6 +63,8 @@ jobs:
         uses: dlang-community/setup-dlang@v1
         with:
           compiler: ${{ matrix.dc }}
+      - name: Install Doveralls (code coverage tool)
+        run: dub fetch doveralls
         
       - name: DUB unit tests with coverage
         run: dub test --coverage