[Paragraph Block] add font family support

[MaggieCabrera]

Description

Closes #36234

This PR adds font family support to the paragraph block. I don't know if there's a reason why this wasn't added before, but I agree with the reasons over at #36234. I've encountered a few cases where the paragraph block was the best option in terms of markup but wanted the text to look like a heading block instead.

How has this been tested?

Tested this using Seedlet Blocks.
To test use a theme that provides multiple fonts, check that you can change the font family to the paragraph block, it should look like the screenshot.

Screenshots

Types of changes

New feature (non-breaking change which adds functionality)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[aaronrobertshaw]

I don't know if there's a reason why this wasn't added before, but I agree with the reasons over at #36234.

There was a desire to delay surfacing this block support until we have a better way to manage custom fonts. A summary from a chat with @mtias can be found in #34064 (comment)

My understanding was we'd only keep font-family as an option for the blocks that already had opted into that support and ensure it wasn't displayed as a default control within the typography panel.

[MaggieCabrera]

There was a desire to delay surfacing this block support until we have a better way to manage custom fonts. A summary from a chat with @mtias can be found in #34064 (comment)

My understanding was we'd only keep font-family as an option for the blocks that already had opted into that support and ensure it wasn't displayed as a default control within the typography panel.

Should we revert this then? I wish we could have this in the block markup even if the UI doesn't show it to the user

[apeatling]

I think we should revert this based on previous conversations linked. Let's please get more reviews and ping folks working in this area before merging, we are happy to help.

[alan-la-chen-478]

Based on the committed file, a temporarily hack:

add_filter('register_block_type_args', function($args, $name) {
    if ($name == 'core/paragraph') {
        $args['supports']['typography']['__experimentalFontFamily'] = true;
    }

    return $args;
}, 10, 2);

or, to show up as default controls:

add_filter('register_block_type_args', function($args, $name) {
    if ($name == 'core/heading') {
        $settings['supports']['typography']['__experimentalFontFamily'] = true;
        $settings['supports']['typography']['__experimentalDefaultControls']['fontFamily'] = true;
    }

    return $args;
}, 10, 2);

will do the trick for now until official solution.

[kevingobert]

@alan-la-chen-478 Thank
I tested your small hack but I have not core blocks in the filter. I have WooCommerce blocks and Gravity block but I don't see core/heading and core/paragraph. Do you know the reason ?

Edit:

I found a solution. I did it in JavaScript and it works

const { addFilter } = wp.hooks
import { set as _set } from 'lodash'

function addFontFamillySupport(settings) {
  const names = ['core/heading', 'core/paragraph']

  if(names.includes(settings.name))
    settings = _set(settings, 'supports.typography.__experimentalFontFamily', true)
  
  return settings
}

addFilter('blocks.registerBlockType', 'koa/font-familly-supports', addFontFamillySupport)