add concurrency

.github/workflows/Tasmota_build_master.yml

@@ -7,6 +7,11 @@ on:
     - '.github/**' # Ignore changes towards the .github directory
     - '**.md' # Do no build if *.md files changes
 
+# Ensures that only one deploy task per branch/environment will run at a time.
+concurrency:
+  group: environment-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   base-images:
     runs-on: ubuntu-latest