fix: Spelling

Author: n0nSmoker

README.md

@@ -340,7 +340,7 @@ By default the library can serialize the following types:
  - dict (if values and keys are one of types mentioned above, or inherit one of them)
  - any Iterable (if types of values are mentioned above, or inherit one of them)
  ```
- If you want to add serialization of any other type or redefine the default behaviour.
+ If you want to add serialization of any other type or redefine the default behavior.
  You should add something like this:
 
 ```python