docs: Fix typos and clarify instructions in README.md

Author: n0nSmoker

README.md

@@ -75,7 +75,7 @@ class ModernModel(Base, SerializerMixin):
 ```
 
 Both styles work identically with **SerializerMixin** - use whichever style you prefer!
-In order to change the default output you shuld pass tuple of fieldnames as an argument
+In order to change the default output you should pass tuple of fieldnames as an argument
 
 - If you want to exclude or add some extra fields (not from database)
   You should pass `rules` argument
@@ -433,7 +433,7 @@ import pytz
 item.to_dict(timezone=pytz.timezone('Europe/Moscow'))
 ```
 - But if you do not want to write this code in every function, you should define
-  timezone logic in your custom mixin (how to use customized mixin see [Castomization](#Castomization))
+  timezone logic in your custom mixin (how to use customized mixin see [Custom formats](#Custom-formats))
  ```python
 import pytz
 from sqlalchemy_serializer import SerializerMixin
@@ -523,7 +523,7 @@ serialize_only = ('some_field')  # <--- WRONG it is actually not a tuple
 ```
 
 # Tests
-To run tests and see tests coverage report just type the following command:(doker and doker-compose should be installed on you local machine)
+To run tests and see tests coverage report just type the following command:(docker and docker-compose should be installed on you local machine)
 ```bash
 make test
 ```