Code formatting and updated pre-commit hook

[aj3sh]

• Update pre-commit config file (Replaced black with darker)
• Updated CI for ignoring E203 and W503 warnings on flake8
• Formatted code as suggested by flake8

[aj3sh]

Still getting a warning on flake8. I will create and link an issue for it.

./nepali/datetime/parser/validators.py:141:1: C901 'transform' is too complex (21)
1     C901 'transform' is too complex (21)