Pyspellchecker

* Backwards Combatibility Change:
* `spell.candidates` and `spell.correction` now return `None` if there are no valid corrections or candidates
* Remove misspelled words from [issue 120](https://github.com/barrust/pyspellchecker/issues/120)
* Update all default language dictionaries after updating the minimum frequency to 50 in `scripts/build_dictionary.py`
* Fix float("nan") issue; see [125](https://github.com/barrust/pyspellchecker/issues/125)
* Include [Wikipedia's common typo list](https://en.wikipedia.org/wiki/Wikipedia:Lists_of_common_misspellings/For_machines) to the exclude listing; see [#124](https://github.com/barrust/pyspellchecker/issues/124)
* Added `Arabic` language support; see [129](https://github.com/barrust/pyspellchecker/pull/129)

* Added class method to be able to get a listing of all supported languages
* Added type hinting
* Updated English dictionary to remove incorrect `cie` words; see [112](https://github.com/barrust/pyspellchecker/issues/112)

* Add ability to load multiple languages at once; [see discussion](https://github.com/barrust/pyspellchecker/discussions/97)
* Fix default tokenizer to not enforce lower case; [99](https://github.com/barrust/pyspellchecker/issues/99)

* Deprecated `spell.word_probability` since the name makes it seem that it is building a true probability; use `spell.word_usage_frequency` instead
* Added Russian language dictionary; [91](https://github.com/barrust/pyspellchecker/pull/91) Thanks [sviperm](https://github.com/sviperm)
* Include `__iter__` to both the `SpellChecker` and `WordFrequency` objects

* Removed **python 2.7** support
* Updated automated `scripts/build_dictionary.py` script to support adding missing words
* Updated `split_words()` to attempt to better handle punctuation; [84](https://github.com/barrust/pyspellchecker/issues/84)
* Load pre-built dictionaries from relative location for use in `PyInstaller` and other executable tools; [64](https://github.com/barrust/pyspellchecker/issues/64)

* ***NOTE:*** Last planned support for **Python 2.7**
* All dictionaries updated using the `scripts/build_dictionary.py` script