CI: add workflow to cancel previous runs

Author: TFSThiagoBR98

.github/workflows/emscripten.yml

@@ -9,6 +9,12 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
+    - name: Cancel previous runs
+      uses: styfle/cancel-workflow-action@0.9.1
+      with:
+          access_token: ${{ github.token }}
+          all_but_latest: true
+
     - name: Checkout Base Repo
       uses: actions/checkout@v2