switch to pnpm from yarn (#31)

Author: kazupon

.github/workflows/lint.yml

@@ -22,12 +22,16 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+      - name: Install pnpm
+        uses: pnpm/action-setup@v2.0.1
+        with:
+          version: 6.17.0
       - name: Setup Node.js v14.x
         uses: actions/setup-node@v2
         with:
           node-version: 14
-          cache: 'yarn'
+          cache: 'pnpm'
       - name: Install
-        run: yarn install
+        run: pnpm install
       - name: Lint
-        run: yarn lint
+        run: pnpm lint

.github/workflows/test.yml

@@ -26,12 +26,16 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+      - name: Install pnpm
+        uses: pnpm/action-setup@v2.0.1
+        with:
+          version: 6.17.0
       - name: Setup Node.js ${{ matrix.node }}
         uses: actions/setup-node@v2
         with:
           node-version: ${{ matrix.node }}
-          cache: 'yarn'
+          cache: 'pnpm'
       - name: Install
-        run: yarn install
+        run: pnpm install
       - name: Test
-        run: yarn test
+        run: pnpm test