feat(core): add getSupportedPlatforms method

src/@ionic-native/core/decorators.spec.ts

@@ -24,7 +24,8 @@ class TestObject {
   pluginName: 'TestPlugin',
   pluginRef: 'testPlugin',
   repo: '',
-  plugin: 'cordova-plugin-my-plugin'
+  plugin: 'cordova-plugin-my-plugin',
+  platforms: ['Android', 'iOS']
 })
 class TestPlugin extends IonicNativePlugin {
 
@@ -85,6 +86,10 @@ describe('Regular Decorators', () => {
       expect(TestPlugin.getPlugin()).toEqual(window.testPlugin);
     });
 
+    it('should return supported platforms', () => {
+      expect(TestPlugin.getSupportedPlatforms()).toEqual(['Android', 'iOS']);
+    });
+
   });
 
   describe('Cordova', () => {

src/@ionic-native/core/ionic-native-plugin.ts

@@ -38,4 +38,9 @@ export class IonicNativePlugin {
    */
   static getPluginInstallName(): string { return; }
 
+  /**
+   * Returns the plugin's supported platforms
+   */
+  static getSupportedPlatforms(): string[] { return; }
+
 }