Dotty-dict

- Dropped pipenv usage
- Introduced poetry dependency manager
- Bumpped dependencies versions
- Introduced Py39,Py310,PyPy38,PyPy39 test environments
- Converted Polish characters to an ASCII substitute
- Updated CONTRIBUTING.rst
- Fixed minor lint errors
- Fixed NoneType iteration exception
- fixed flaky caching test

Added

* LRU Cache Dysproz
* Native support for lists, including multidimensional lists Dysproz

`dotty_l` is now deprecated. Use `dotty` instead.

Changed

* Fix code blocks in README.md linusg

- Adds support for accessing root level elements aneeshd16

- Add compatibility with MicroPython amotl
- Fix "setdefault" wrapper when nested key already exists amotl

added
* support for accessing lists inside dotty dict