chore: Add 'Cancel Previous Runs' step (#840)

Co-authored-by: Kent C. Dodds <me+github@kentcdodds.com>

Author: MichaelDeBoey

.github/workflows/validate.yml

@@ -21,6 +21,11 @@ jobs:
         react: [latest, next, experimental]
     runs-on: ubuntu-latest
     steps:
+      - name: 🛑 Cancel Previous Runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ secrets.GITHUB_TOKEN }}
+
       - name: ⬇️ Checkout repo
         uses: actions/checkout@v2
 
@@ -53,6 +58,11 @@ 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/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ secrets.GITHUB_TOKEN }}
+
       - name: ⬇️ Checkout repo
         uses: actions/checkout@v2