add foundry step

Author: varunsrin

.github/workflows/ci.yml

@@ -61,6 +61,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
+      - name: Install foundry
+        uses: foundry-rs/foundry-toolchain@v1
+        with:
+          version: nightly
+
       - name: Run Slither
         uses: crytic/slither-action@main
         id: slither # Required to reference this step in the next step.