Add a non-breaking space at the end of the personalization tag

When a text block contains only a personalization tag, WP renderer removes the block.
Adding a non-breaking space is a workaround solving this issue.
[MAILPOET-6396]

packages/js/email-editor/src/blocks/core/rich-text.tsx

@@ -97,7 +97,7 @@ function PersonalizationTagsButton( { contentRef }: Props ) {
 				let richTextValue = create( { html: blockContent } );
 				richTextValue = insert(
 					richTextValue,
-					create( { html: `<!--${ tag }-->` } ),
+					create( { html: `<!--${ tag }-->&nbsp;` } ), // Add a non-breaking space to avoid an issue when WP renderer removes blog containing only a comment
 					start,
 					end
 				);