Fix typos

Author: Artem Innokentiev

EN.md

@@ -11,15 +11,15 @@
   - [Docstrings](#docstrings)
 - [About Pull Request](#about-pull-request)
   - [Creating Pull Request](#creating-pull-request)
-  - [Refactoring and Pull Requests](#Refactoring-and-pull-request)
+  - [Refactoring and Pull Requests](#refactoring-and-pull-request)
   - [Pull Request Size](#pull-request-size)
 - [About tooling](#about-tooling)
-  - [Testing (pytest)](#Testing-pytest)
+  - [Testing (pytest)](#testing-pytest)
   - [Package manager (poetry)](#package-manager-poetry)
   - [Code formatting (Black)](#code-formatting-black)
   - [Imports formatting (isort)](#imports-formatting-isort)
   - [Linter (flake8)](#linter-flake8)
-  - [Type checker (mypy)](#type checker-mypy)
+  - [Type checker (mypy)](#type-checker-mypy)
   - [Pre-commit hooks (pre-commit)](#pre-commit-hooks-pre-commit)
 - [Other](#other)
   - [REST API Documentation](#rest-api-documentation)