Add workflow_dispatch to github actions

Author: deepy

.github/workflows/build-examples.yml

@@ -1,5 +1,5 @@
 name: Build Examples
-on: [push, pull_request]
+on: [push, pull_request, workflow_dispatch]
 jobs:
   examples:
     runs-on: ubuntu-latest

.github/workflows/build.yml

@@ -1,5 +1,5 @@
 name: Build
-on: [push, pull_request]
+on: [push, pull_request, workflow_dispatch]
 jobs:
   linux:
     runs-on: ubuntu-latest

.github/workflows/gradle-wrapper-validation.yml

@@ -1,5 +1,5 @@
 name: "Validate Gradle Wrapper"
-on: [push, pull_request]
+on: [push, pull_request, workflow_dispatch]
 
 jobs:
   validation: