Use the Format API to add SVG in RichText

svg-format-demo.js

( ( {
	blockEditor: { RichTextToolbarButton },
	element: { createElement },
	richText: { insertObject, registerFormatType, remove },
} ) => {
	const formatName = 'svg-format-demo/one';
	const format = {
		title: 'SVG Format Demo',
		tagName: 'u',
		contentEditable: false,
		className: 'svg-format-demo--one',
		attributes: {
				className: 'class',
		},
		edit: ( { isObjectActive, onChange, value } ) => {
			const onClick = () => {
				if ( isObjectActive )
					return onChange( remove( value ) );

				const toInsert = {
					type: formatName,
					attributes: {
						viewBox: '0 0 24 24',
					},
					innerHTML: `<svg viewBox="0 0 24 24" style="width:1em;height:1em;fill:none;stroke:currentColor;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;"><path d="M16 7h.01"/><path d="M3.4 18H12a8 8 0 0 0 8-8V7a4 4 0 0 0-7.28-2.3L2 20"/><path d="m20 7 2 .5-2 .5"/><path d="M10 18v3"/><path d="M14 17.75V21"/><path d="M7 18a6 6 0 0 0 3.84-10.61"/></svg>`,
				}
				onChange( insertObject( value, toInsert ) );
			};
			return createElement(
				RichTextToolbarButton, {
					isActive: isObjectActive,
					icon: 'art',
					title: 'Put a bird on it',
					onClick,
				}
			)
		}
	};
	wp.richText.registerFormatType( formatName, format );
} )( wp );

svg-format-demo.php

<?php
/*
Plugin Name: SVG Format Demo
*/

add_action( 'init', function () {
  wp_register_script(
    'svg-format-demo-js',
    plugins_url( 'svg-format-demo.js', __FILE__ ),
    array( 'wp-rich-text', 'wp-element', 'wp-block-editor' )
  );
});

add_action( 'enqueue_block_editor_assets', function () {
  wp_enqueue_script( 'svg-format-demo-js' );
});