Fix the regexp performance issue

Also move the addHoverClass implementation into the rebuild stage.
So if there is still some corner case we have not handled, it will
only affect the replayer part of rrweb.

src/types.ts

@@ -32,6 +32,7 @@ export type elementNode = {
 export type textNode = {
   type: NodeType.Text;
   textContent: string;
+  isStyle?: true;
 };
 
 export type cdataNode = {