Your reviewers can upload video reviews inside the Review Widget. You have to enable this feature inside the Product Reviews app, Settings > Review Widget > Widget Addons > Review Videos.

Review videos and pictures cannot be uploaded inside the in-email review form (because the SMTP email protocol doesn't allow this). Your reviewers will go to the product page with the pre-filled & pre-opened Review Widget to add a review video or review photos.

Review Widget with video review

Adding a video review