[feat] Show Multiple Images as a Carousel

[superextinct]

This PR enables editors to display multiple images in a carousel.

Changes

• Adds a new Gallery entry type in Craft CMS with an images field and auto-generated title (e.g. "3 Images")
• Adds the Gallery entry type to the modules matrix field and the textEntryTypes rich-text field so editors can insert galleries anywhere
• Adds a <gallery-carousel> custom element powered by Splide
• Lazily loads Splide via dynamic import() to keep the initial JS bundle small
• Renders each image at a 3:2 crop with caption, credit
  (pipe-separated), and optional secondary rich-text caption
• Gallery breaks out of the text column to full viewport width in the columns rich-text layout
• Refactors the srcset macro: Stops generating srcset urls for unsupported image formats (gif/svg), removes "unkown" from the output

[harryfk]

Yay, web components! I took a look, good stuff! Noticed a few minor things:

• There doesn’t seem to be any margin top/bottom for me, it goes right to the edge of the next module
• Long secondary image captions stretch the slide container, causing gaps, instead of breaking into multiple lines
• I double-checked the figma and apparently the grey captions should be uppercased

Screenshot showing missing margins and the caption issue:

I’m also wondering whether we should indeed crop the images to a fixed aspect ratio … this will cause issues with portrait images, for sure. On Publix we have a similar slider and the images all get the same height, while keeping their original ratio. Maybe this would be a better fit?

[superextinct]

Thanks for being thorough, @harryfk! I've fixed the spacing and width issues and also modified the transform to use the asset's original aspect ratio:

[harryfk]

Woah, that looks ace! I’ll quickly check it locally.

[harryfk]

Coool, this looks much better now! I’ve tested it locally and it all looks great to me. In my RSS reader the markup structure with slides as a list and then also another list in the figcaption is a bit odd, but also makes sense … I’m leaning towards keeping it like this.

Also works great as a standalone module! All good from my end.