Storybook: fix gallery function in carousel lightboxes

[stephiescastle]

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Description

Noticed when exploring #41 that the fancyboxGallery argument wasn't working as expected in Image carousels.

• fixed the BlockImageLightboxTemplate to accept two arguments
• updated index.html to use copied HTML from storybook for the image carousel and image block. This also now allows us to test fancybox in index.html as we didn't have any usage of it on the test page before.

Instructions to test

1. npm run storybook
2. Check the BlockImageCarousel or BlockImageGallery stories. When opening the lightbox, you should be able to browse the rest of the images within the lightbox
3. npm run dev
4. Check the index page and test the lightbox on BlockImage and BlockImageCarousel.

Tested in the following environments/browsers:

Operating System

• macOS
• iOS
• iPadOS
• Windows

Browser

• Chrome
• Firefox ESR
• Firefox
• Safari
• Edge

[stephiescastle]

@Scotchester I've fixed the caption rendering in fancybox and also added some more arg descriptions to BaseImageCaption. Thanks for catching that!

[Scotchester]

Great catch! Fix is working great.