feat(twa) add TWA check function

.gitignore

@@ -12,3 +12,4 @@ npm-*.log
 .jshintrc
 .DS_Store
 stats.json
+.vscode

modules/browser/BrowserCapabilities.js

@@ -61,6 +61,15 @@ export default class BrowserCapabilities extends BrowserDetection {
             || this.isOpera();
     }
 
+    /**
+     * Checks whether current running context is a Trusted Web Application.
+     *
+     * @returns {boolean} Whether the current context is a TWA.
+     */
+    isTwa() {
+        return 'matchMedia' in window && window.matchMedia('(display-mode:standalone)').matches;
+    }
+
     /**
      * Checks if the current browser is supported.
      *