[Quote, Pullquote Blocks] Allow theme.json customizations of the citation fields

[kjellr]

Currently, theme.json does not let you style the citation field for the Quote and Pullquote blocks.

It should be possible to (for example), set a font size for the main quote, and set a specific font size for the citation as well. Or to use different fonts for each. Here's some pseudocode for example:

"core/pullquote": {
	"typography": {
		"fontFamily": "var(--wp--preset--font-family--source-serif-pro)",
		"fontSize": "var(--wp--preset--font-size--huge)",
		"fontWeight": "300"
	},
	"citation": {
		"typography": {
			"fontFamily": "var(--wp--preset--font-family--system)",
			"fontSize": "var(--wp--preset--font-size--small)",
			"fontStyle": "italic"
		}
	}
}

Here's an example of what we'd like to achieve for the pullquote block in Twenty Twenty-Two, but cannot at the moment:

The main issue in that specific case is that I cannot use one font for the quote, and another font for the citation.

[ZebulanStanphill]

It's worth noting that there have been plans to convert the Quote (and presumably also the Pullquote) to use nested blocks (#15486), and one of the things that would likely change alongside that is the markup of the blocks, in order to match the latest WHATWG spec. See https://github.com/WordPress/gutenberg/pull/25892/files#r589615279. Not sure if that has any effect on this issue, but I figured I'd bring it up in case it did,

[carolinan]

@scruffian 👋 Do you think citation / cite should be added to elements?

[scruffian]

Yes I do. Would you like to create a PR for it? :)

[carolinan]

Yes I can try, there should be enough reference in the other elements changes.

[scruffian]

This was closed by #43543