TYP: annotation of __init__ return type (PEP 484) (pandas/core/arrays)
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

According to [documentation](https://pandas.pydata.org/docs/dev/development/contributing_codebase.html#type-hints) pandas uses [PEP484](https://www.python.org/dev/peps/pep-0484/) for type hints.
PEP484 states that `__init__` function should have `-> None` return type annotation.
In this PR I added return type annotation to `__init__` functions in `pandas/core/arrays` module

Hello @EkaterinaKuzkina! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

































There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2022-03-07 22:27:29 UTC thanks @EkaterinaKuzkina 