Fix GitHub Actions workflow by adding pnpm setup and caching

Author: bvoo

.github/workflows/main.yml

@@ -37,7 +37,25 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: lts/*
-          cache: 'pnpm' # Set this to npm, yarn or pnpm.
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v2
+        with:
+          version: latest
+
+      - name: Get pnpm store directory
+        id: pnpm-cache
+        shell: bash
+        run: |
+          echo "STORE_PATH=$(pnpm store path)" >> $GITHUB_OUTPUT
+
+      - name: Setup pnpm cache
+        uses: actions/cache@v3
+        with:
+          path: ${{ steps.pnpm-cache.outputs.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
 
       - name: install Rust stable
         uses: dtolnay/rust-toolchain@stable # Set this to dtolnay/rust-toolchain@nightly