Adds Github Action to validate Gradle Wrapper (WordPress#46247)

Author: oguzkocer

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

@@ -0,0 +1,10 @@
+name: 'Validate Gradle Wrapper'
+on: [push, pull_request]
+
+jobs:
+    validation:
+        name: 'Validation'
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v2
+            - uses: gradle/wrapper-validation-action@v1