Provide support for proper type hints - change of model definition (non breaking)

• Changed notation in Model definition -> now use name = ormar.Field() not name: ormar.Field()
• Note that old notation is still supported but deprecated and will not play nice with static checkers like mypy and pydantic pycharm plugin
• Type hint docs and test
• Use mypy for tests also not, only ormar package
• Fix scale and precision translation with max_digits and decimal_places pydantic Decimal field
• Update docs - add best practices for dependencies
• Refactor metaclass and model_fields to play nice with type hints
• Add mypy and pydantic plugin to docs
• Expand the docs on ManyToMany relation