Merge branch Davi0kProgramsThings:fix/refactoring into branch bitfinexcom:master.

[Davi0kProgramsThings]

Description

PR introduces isort, black and flake8 in the project's development stack.
It also introduces support for pre-commit (see .pre-commit-config.yaml).
New steps has been added to the build action in bitfinex-api-py-ci.yml.

README has been updated with a brief chapter on how to set up pre-commit.

The project won't support pylint anymore.

Motivation and Context

From now on, developers will no longer need to write code that complies to PEP8 theirself.
pre-commit will take care of formatting the project's code base to fit the PEP8 style guidelines.
The developers will only be responsible for ensuring that flake8 does not return any error.

Related Issue

PR fixes the following issue: -

Type of change

• Bug fix (non-breaking change which fixes an issue);
• New feature (non-breaking change which adds functionality);
• Breaking change (fix or feature that would cause existing functionality to not work as expected);
• This change requires a documentation update;

Checklist:

• I've done a self-review of my code;
• I've made corresponding changes to the documentation;
• I've made sure my changes generate no warnings;
• mypy returns no errors when run on the root package;

• I've run black to format my code;
• I've run isort to format my code's import statements;
• flake8 reports no errors when run on the entire code base;