add helpful website link to ast viewer

Author: Emyrk

README.md

@@ -52,4 +52,8 @@ ts.ApplyMutations(
 	config.EnumLists,
 )
 output, _ := ts.Serialize()
-```
+```
+
+# Helpful notes
+
+An incredible website to visualize the AST of typescript: https://ts-ast-viewer.com/