Add androidTargetSdkVersion as an option to update the Android SDK (#298)

* Add androidTargetSdkVersion as an option to update the Android SDK API level

* Fix build script

* Update default value

* Add JAVA_HOME

* Use Unity_path

* Update src/model/android-versioning.test.ts

Co-authored-by: Webber Takken <webber@takken.io>

* Correct JAVA_HOME

* Use unity_path

* Update JAVA_HOME to use path found from 2020.3

* Dynamically determine JAVA_HOME

* Update path determination

Co-authored-by: Webber Takken <webber@takken.io>

src/model/input.ts

@@ -75,6 +75,10 @@ class Input {
     return core.getInput('androidKeyaliasPass') || '';
   }
 
+  static get androidTargetSdkVersion() {
+    return core.getInput('androidTargetSdkVersion') || '';
+  }
+
   static get allowDirtyBuild() {
     const input = core.getInput('allowDirtyBuild') || false;