chore(foundry): add foundry-toolchain mention (#340)

Author: zerosnacks

src/pages/sdk/foundry/index.mdx

@@ -108,6 +108,18 @@ Tempo's contract verifier is Sourcify-compatible. Configure verification with `V
 
 The `[etherscan]` table in `foundry.toml` is for Etherscan-style verifiers, not Tempo's verifier.
 
+### Using `foundry-toolchain` in your CI
+
+Use the [`foundry-toolchain`](https://github.com/foundry-rs/foundry-toolchain) GitHub Action to install Foundry in your CI.
+Tempo support is included in Foundry, so no special configuration is needed.
+
+```yaml
+- name: Install Foundry
+  uses: foundry-rs/foundry-toolchain@v1
+  with:
+    version: nightly
+```
+
 ## Use Foundry for your workflows
 
 All standard Foundry commands are supported out of the box.