Enable the dropcap feature by modifying the theme.json

enable-dropcap.php

 <?php

/**
 * Add drop cap support to the theme.json file.
 * 
 * @param array $theme_json The theme.json json.
 * 
 * @link https://developer.wordpress.org/block-editor/developers/themes/theme-json/#typography
*/
add_filter( 'wp_theme_json_data_theme', function( $theme_json ) {

	$json = $theme_json->get_data();

	$json['settings']['typography'] = [ 'dropCap' => true ];

	return $theme_json->update_with( $json );
}, 10, 1 );