Cache multiple target directories from 'target-dir'

.github/workflows/selftest.yml

@@ -24,8 +24,13 @@ jobs:
       - uses: ./
         with:
           cache-on-failure: true
+          target-dir: |
+            target/
+            wasm-workspace/target/
 
       - run: |
           cargo install cargo-deny --locked
           cargo check
-          cargo test
+          cargo test
+          rustup target install wasm32-unknown-unknown
+          cd wasm-workspace && cargo check