chore: add JSDoc to MediaChange (#920)

Author: CaerusKaru

src/lib/core/media-change.ts

@@ -14,13 +14,20 @@ export class MediaChange {
   property: string = '';
   value: any;
 
-  constructor(public matches = false,       // Is the mq currently activated
-              public mediaQuery = 'all',    // e.g.   (min-width: 600px) and (max-width: 959px)
-              public mqAlias = '',          // e.g.   gt-sm, md, gt-lg
-              public suffix = ''            // e.g.   GtSM, Md, GtLg
-  ) { }
+  /**
+   * @param matches whether the mediaQuery is currently activated
+   * @param mediaQuery e.g. (min-width: 600px) and (max-width: 959px)
+   * @param mqAlias e.g. gt-sm, md, gt-lg
+   * @param suffix e.g. GtSM, Md, GtLg
+   */
+  constructor(public matches = false,
+              public mediaQuery = 'all',
+              public mqAlias = '',
+              public suffix = '') {
+  }
 
-  clone() {
+  /** Create an exact copy of the MediaChange */
+  clone(): MediaChange {
     return new MediaChange(this.matches, this.mediaQuery, this.mqAlias, this.suffix);
   }
 }