Make code preview read-only. Relates to #104

Author: dannyvankooten

includes/views/parts/admin-field-wizard.php

@@ -60,7 +60,7 @@
 
 		<p>
 			<label for="mc4wp-fw-preview"><?php _e( 'Generated HTML', 'mailchimp-for-wp' ); ?></label>
-			<textarea class="widefat" id="mc4wp-fw-preview" rows="5"></textarea>
+			<textarea class="widefat" id="mc4wp-fw-preview" rows="5" readonly></textarea>
 		</p>
 
 	</div>