chore: Add 'Cancel Previous Runs' step (#258)

Co-authored-by: Kent C. Dodds <[email protected]>

.github/workflows/validate.yml

@@ -20,6 +20,11 @@ jobs:
         node: [10.14, 10, 12, 14, 15]
     runs-on: ${{ matrix.os }}
     steps:
+      - name: 🛑 Cancel Previous Runs
+        uses: styfle/[email protected]
+        with:
+          access_token: ${{ secrets.GITHUB_TOKEN }}
+
       - name: ⬇️ Checkout repo
         uses: actions/checkout@v2
 
@@ -47,6 +52,11 @@ jobs:
       contains('refs/heads/master,refs/heads/beta,refs/heads/next,refs/heads/alpha',
       github.ref) && github.event_name == 'push' }}
     steps:
+      - name: 🛑 Cancel Previous Runs
+        uses: styfle/[email protected]
+        with:
+          access_token: ${{ secrets.GITHUB_TOKEN }}
+
       - name: ⬇️ Checkout repo
         uses: actions/checkout@v2