PluginPostPublishPanel uses icon and inherits from registerPlugin

[ryanwelcher]

Description

This PR updates the PluginPostPublishPanel SlotFill to accept an icon or inherit from registerPlugin()

Screenshots

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.

[ryanwelcher]

Confirm that custom SVGs are rendered in greyscale

[ryanwelcher]

@mapk wondering if you can sign off on this PR as well?

[mapk]

@ryanwelcher Can you guide me through some steps to test this? How do I get a custom panel to show in the post-publish slideout?

[ryanwelcher]

@mapk it might be easiest to install this plugin I wrote for a talk I gave on SlotFill - https://github.com/ryanwelcher/the-gutenberg-slotfill-system. It demos all of the slots and if you have this branch active and built, you'll see the icons.

[gziolo]

Nice work. Thanks for sorting it out 👍

I tested with:

( function() {
	var el = wp.element.createElement;
	var Fragment = wp.element.Fragment;
	var __ = wp.i18n.__;
	var registerPlugin = wp.plugins.registerPlugin;
	var PluginPostPublishPanel = wp.editPost.PluginPostPublishPanel;
	var PluginPrePublishPanel = wp.editPost.PluginPrePublishPanel;

	function PanelContent() {
		return el(
			'p',
			{},
			__( 'Here is the panel content!' )
		);
	}

	function MyPublishPanelPlugin() {
		return el(
			Fragment,
			{},
			el(
				PluginPrePublishPanel,
				{
					className: 'my-publish-panel-plugin__pre',
					title: __( 'My pre publish panel' )
				},
				el(
					PanelContent,
					{}
				)
			),
			el(
				PluginPostPublishPanel,
				{
					className: 'my-publish-panel-plugin__post',
					title: __( 'My post publish panel' )
				},
				el(
					PanelContent,
					{}
				)
			)
		);
	}

	registerPlugin( 'my-publish-panel-plugin', {
		icon: 'palmtree',
		render: MyPublishPanelPlugin
	} );
} )();

@mapk - I copied it over from the existing plugin which we use for e2e tests and can be activated in the plugins section for the default Gutenberg env:

However, I had to add the icon property. We might want to update the e2e test as well to have it covered.