Cache crate dependencies on branches (#100)

* Cache crate dependencies on branches

* Switch to actions/cache@v3

Author: elliottt

.github/workflows/main.yml

@@ -194,6 +194,18 @@ jobs:
       with:
         name: engine-release
 
+    - name: Cache build
+      uses: actions/cache@v3
+      with:
+        path: |
+          ~/.cargo/bin/
+          ~/.cargo/registry/index/
+          ~/.cargo/registry/cache/
+          ~/.cargo/git/db/
+          target/
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      if: github.ref != 'refs/heads/main' && !startsWith(github.ref, 'refs/tags/v')
+
     # Build `js-compute-runtime`
     - run: PREBUILT_ENGINE=engine-release/js-compute-runtime.wasm $CENTOS cargo build --release