fix: show all images in gallery

[ablax]

Description

I have venture installed and I have imported products as described by venture with the appropriate images, but only the main image was to be seen on the product's main page.

Related Issue

Closes https://github.com/vuestorefront-community/vendure/issues/195

Motivation and Context

Allows all pictures to be seen on product pages.

How Has This Been Tested?

I have published a custom npm version of this package and tested with it. Decided to share with the rest as well.

Screenshots (if appropriate):

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.