Release v0.2.1

• 83eaa1d chore: update lib patch version to 0.2.1
• 2bd3745 chore: update x-injection to latest & fix issue with the internal error classes naming
• aa97bea chore(readme): add codecov badge and use classic badges styles
• a8194da ci: add integration with Codecov
• e98ee8b refactor: remove the X prefix from the error classes
• 1e4ab31 config: add noImplicitOverride TS rule
• aadff91 chore(readme): fix unit test examples - 2
• d4d9e33 fix(readme): unit test example
• 8896b45 chore(readme): add unit test examples