CI: cargo cache (#3)

.github/workflows/ci.yml

@@ -15,6 +15,14 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - uses: actions/cache@v2
+      with:
+        path: |
+          ~/.cargo/registry
+          ~/.cargo/git
+          target
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
     - name: lint
       run: cargo fmt -- --check
 
@@ -33,6 +41,14 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - uses: actions/cache@v2
+      with:
+        path: |
+          ~/.cargo/registry
+          ~/.cargo/git
+          target
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
     - name: install wasm-pack
       run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh