Add pnpm to GitHub Action

Based on https://pnpm.io/continuous-integration#github-actions

.github/workflows/node.js.yml

@@ -17,11 +17,14 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+    - uses: pnpm/action-setup@v2.2.2
+      with:
+        version: 6
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v2
       with:
         node-version: ${{ matrix.node-version }}
-    - run: pnpm i --no-optional
+    - run: pnpm i --no-optional --no-frozen-lockfile
     - run: wget -q -O factorio.tar.gz https://www.factorio.com/get-download/latest/headless/linux64 && tar -xf factorio.tar.gz && rm factorio.tar.gz
     - run: node packages/lib/build_mod --source-dir packages/slave/lua/clusterio_lib --output-dir temp/test/sharedMods
     - run: wget -q -O temp/test/sharedMods/subspace_storage_1.99.8.zip -L https://github.com/clusterio/subspace_storage/releases/download/1.99.6/subspace_storage_1.99.8.zip
@@ -41,8 +44,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+    - uses: pnpm/action-setup@v2.2.2
+      with:
+        version: 6
     - uses: actions/setup-node@v2
       with:
         node-version: 16.x
-    - run: pnpm i --no-optional
+    - run: pnpm i --no-optional --no-frozen-lockfile
     - run: pnpm run lint