tour: improve chapter2 lesson4

moonbit-tour/tour/chapter2_data_types/lesson4_newtype/index.md

@@ -2,5 +2,5 @@
 
 Newtypes are similar to enums with only one constructor (with the same name as the newtype itself). You can use the constructor to create values of the newtype and use `._` to extract the internal representation. 
 
-*Pattern matching* can also be used.
+You can also use *pattern matching* with newtypes.