Cache cargo registry and build target directory in CI (#78)

* try caching cargo registry and build

* trigger build

* try fixing path

* force build

* try different cache key

* try rebuild

.github/workflows/rust.yml

@@ -19,6 +19,18 @@ jobs:
           components: rustfmt, clippy
           override: true
 
+      - name: Cache Cargo Registry
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/registry
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.toml') }}
+
+      - name: Cache Cargo Build Target
+        uses: actions/cache@v1
+        with:
+          path: tokenizers/target
+          key: ${{ runner.os }}-cargo-build-${{ hashFiles('**/Cargo.toml') }}
+
       - name: Build
         uses: actions-rs/cargo@v1
         with: