Wire new init-script into action

- Copy init-script to Gradle User Home
- Rename init-scripts for consistency and clarity

src/resources/init-scripts/gradle-build-action.github-dependency-graph-gradle-plugin-apply.groovy

@@ -0,0 +1,9 @@
+buildscript {
+  repositories {
+    maven { url "https://plugins.gradle.org/m2/" }
+  }
+  dependencies {
+    classpath "org.gradle:github-dependency-graph-gradle-plugin:0.2.0"
+  }
+}
+apply plugin: org.gradle.github.GitHubDependencyGraphPlugin