FEC-13956: Add window before MediaSource (#774)

### Description of the Changes

Please add a detailed description of the change, whether it's an
enhancement or a bugfix.
If the PR is related to an open issue please link to it.

### CheckLists

- [ ] changes have been done against master branch, and PR does not
conflict
- [ ] new unit / functional tests have been added (whenever applicable)
- [ ] test are passing in local environment
- [ ] Travis tests are passing (or test results are not worse than on
master branch :))
- [ ] Docs have been updated

src/engines/html5/media-source/base-media-source-adapter.ts

@@ -101,7 +101,7 @@ export default class BaseMediaSourceAdapter extends FakeEventTarget implements I
   public static isMSESupported(): boolean {
     // eslint-disable-next-line  @typescript-eslint/ban-ts-comment
     // @ts-ignore
-    const mediaSource = MediaSource || window.WebKitMediaSource;
+    const mediaSource = window.MediaSource || window.WebKitMediaSource;
     // isTypeSupported isn't exist or not a function for old MSE implementation
     return !!mediaSource && typeof mediaSource.isTypeSupported === 'function';
   }