Fix inline link elements bug (#995)

* fix: bug when inlined link elements

* test: update snapshot for test cases

* apply Justin's review suggestions

1. make Mirror's replace function act the same with the original one when there's no existed node to get replaced.
2. when replacing with the link/style elements, keep their existing attributes to prevent potential bugs

packages/rrweb-snapshot/src/snapshot.ts

@@ -1165,7 +1165,6 @@ export function serializeNodeWithId(
       },
       stylesheetLoadTimeout,
     );
-    if (isStylesheetLoaded(n as HTMLLinkElement) === false) return null; // add stylesheet in later mutation
   }
 
   return serializedNode;