Add concurrency control to workflow

Author: roman-dvorak

.github/workflows/platformio-build.yml

@@ -7,6 +7,10 @@ on:
     types: [ created, published ]
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     runs-on: ubuntu-latest