Add workflow_dispatch trigger to workflows from GitHub

Author: cartland

.github/workflows/build.yml

@@ -1,6 +1,9 @@
 name: build
 
-on: [push, pull_request]
+on:
+  workflow_dispatch:
+  push:
+  pull_request:
 
 jobs:
   build:
@@ -22,4 +25,3 @@ jobs:
     - name: build samples
       run: |
         ./gradlew build
-