Site Title Block: Add alignment and tag level support (#22843)

* Add alignment control to the site title block edit function.

* Add support for setting site title tag, and applying text alignment in the editor and front end.

* Fix up classname output, and add a default site title classname.

* Fix PHP linting issues.

packages/block-library/src/site-title/block.json

@@ -5,6 +5,9 @@
 		"level": {
 			"type": "number",
 			"default": 1
+		},
+		"align": {
+			"type": "string"
 		}
 	},
 	"supports": {

packages/block-library/src/site-title/edit.js

@@ -1,23 +1,47 @@
+/**
+ * External dependencies
+ */
+import classnames from 'classnames';
+
 /**
  * WordPress dependencies
  */
 import { useEntityProp } from '@wordpress/core-data';
 import { __ } from '@wordpress/i18n';
 import {
-	PlainText,
+	RichText,
+	AlignmentToolbar,
+	BlockControls,
 	__experimentalBlock as Block,
 } from '@wordpress/block-editor';
 
-export default function SiteTitleEdit() {
+export default function SiteTitleEdit( { attributes, setAttributes } ) {
+	const { level, align } = attributes;
 	const [ title, setTitle ] = useEntityProp( 'root', 'site', 'title' );
+	const tagName = 0 === level ? 'p' : 'h' + level;
+
 	return (
-		<PlainText
-			__experimentalVersion={ 2 }
-			tagName={ Block.h1 }
-			placeholder={ __( 'Site Title' ) }
-			value={ title }
-			onChange={ setTitle }
-			disableLineBreaks
-		/>
+		<>
+			<BlockControls>
+				<AlignmentToolbar
+					value={ align }
+					onChange={ ( nextAlign ) => {
+						setAttributes( { align: nextAlign } );
+					} }
+				/>
+			</BlockControls>
+
+			<RichText
+				tagName={ Block[ tagName ] }
+				placeholder={ __( 'Site Title' ) }
+				value={ title }
+				onChange={ setTitle }
+				className={ classnames( {
+					[ `has-text-align-${ align }` ]: align,
+				} ) }
+				allowedFormats={ [] }
+				disableLineBreaks
+			/>
+		</>
 	);
 }

packages/block-library/src/site-title/index.php

@@ -13,11 +13,19 @@
  * @return string The render.
  */
 function render_block_core_site_title( $attributes ) {
-	$tag_name = 'h1';
+	$tag_name         = 'h1';
+	$align_class_name = empty( $attributes['align'] ) ? '' : ' ' . "has-text-align-{$attributes['align']}";
+
 	if ( isset( $attributes['level'] ) ) {
 		$tag_name = 0 === $attributes['level'] ? 'p' : 'h' . $attributes['level'];
 	}
-	return sprintf( '<%1$s>%2$s</%1$s>', $tag_name, get_bloginfo( 'name' ) );
+
+	return sprintf(
+		'<%1$s class="%2$s">%3$s</%1$s>',
+		$tag_name,
+		'wp-block-site-title' . esc_attr( $align_class_name ),
+		get_bloginfo( 'name' )
+	);
 }
 
 /**