Stabilize Typography Block Supports Keys for WP 6.7

[andrewserong]

Part of:

• Tracking: Addressing Design Tooling Consistency #43241 and
• Tracking: Typography Design Tools Consistency #43242

This issues tracks progress towards stabilizing the typography block support. Note that in order to provide backwards compatibility for block plugins out in the wild, fallback support for the existing __experimental prefixes should be provided.

Stabilize the following typography block supports:

• __experimentalFontFamily → fontFamily
• __experimentalTextDecoration → textDecoration
• __experimentalFontStyle → fontStyle
• __experimentalFontWeight → fontWeight
• __experimentalLetterSpacing → letterSpacing
• __experimentalTextTransform → textTransform
• __experimentalWritingMode → writingMode

Tasks

• Update PHP block support code in lib/block-supports/typography.php to use the non __experimental prefix, falling back to the __experimental prefix if available.
• Update the JS implementations of the typography block supports to point to the non __experimental prefix, falling back to the __experimental prefix if available.
• Update the block.json schema to support the non __experimental prefix, with a note that it is only as of WP 6.7+
• Update the core blocks' block.json files to use the non __experimental prefixes
• For WP 6.7, update the supports documentation to include the new non prefixed versions.
• Once WP 6.7 is released, update the block.json schema to remove the __experimental prefix. Note that the code in WordPress should still support the __experimental prefix, but at this stage, the experimental prefix will be treated as deprecated.

In my opinion, in order to provide the widest possible support for block plugins, I think it could be valuable to provide fallback support for the __experimental in the long-term. In other words, when implementing the fallback ideas above, let's do so in a way that's easy to maintain.