Fixed the code to display the unique images and media_gallery on the product page(#404)

[ymaheshwari1]

Related Issues

#404

closes #404

Short Description of the PR

When changing the value of mergeConfigurableChildren to false the product gallery is not displayed as it should. Using the uniqBy method to display only the unique images in the gallery and also added the media_gallery in the gallery to display all the images in the product gallery.

Screenshots of Visual Changes before/after (if There Are Any)

Pull Request Checklist

• [x] I have updated the Changelog (V1) and mentioned all breaking changes in the public API.
• [ ] I have documented all new public APIs and made changes to existing docs mentioning the parts I've changed so they're up to date.
• [x] I have tested my Pull Request on production build and (to my knowledge) it works without any issues

• [ ] I have followed naming conventions

Upgrade Notes and Changelog

• [x] No upgrade steps required (100% backward compatibility and no breaking changes)
• [x] I've updated the Upgrade notes and Changelog on how to port existing Vue Storefront sites with this new feature

Contribution and Currently Important Rules Acceptance

• [x] I read and followed contribution rules