Add correct engine

[wannaphong]

What does this changes

Add more spelling engine

• Add symspellpy with unigram & bigram from TNC - symspellpy is a Python port of SymSpell v6.5.
• Add Phunspell - A pure Python spell checker utilizing spylls a port of Hunspell.
• Add spell_sent & correct_sent function

Your checklist for this pull request

🚨Please review the guidelines for contributing to this repository.

• Passed code styles and structures
• Passed code linting checks and unit test

[pep8speaks]

Hello @wannaphong! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file pythainlp/spell/__init__.py:

Line 18:1: E402 module level import not at top of file

Comment last updated at 2021-07-21 18:01:48 UTC

[wannaphong]

phunspell is not working with python 3.6.

[coveralls]

Coverage decreased (-0.2%) to 95.837% when pulling 1d55553 on add-correct-engine into ad20a1e on dev.

[wannaphong]

Colab for testing: https://colab.research.google.com/drive/1xgp_txclvolD7O913znqiBjD_7GdtAOM?usp=sharing

[bact]

python 3.6.

Python 3.6 EOL is 2021-12-23, only months away from now.
Maybe have to consider if the next version of PyThaiNLP will going to support 3.6 after its EOL or not.

[wannaphong]

python 3.6.

Python 3.6 EOL is 2021-12-23, only months away from now.
Maybe have to consider if the next version of PyThaiNLP will going to support 3.6 after its EOL or not.

End of support for Python 3.6 in the next version of PyThaiNLP #592