ci: install foundry in pipeline

Author: Luisfc68

.github/workflows/ci.yml

@@ -33,6 +33,11 @@ jobs:
       - name: Install dependencies
         run: npm ci
 
+      - name: "Install Foundry"
+        uses: "foundry-rs/foundry-toolchain@50d5a8956f2e319df19e6b57539d7e2acb9f8c1e" # v1.5.0
+        with:
+          version: stable
+
       - name: Lint contracts
         run: npm run lint:sol