refactor: Reconfigure package imports

[robberwick]

This pull request includes changes to the src/blinkstick/__init__.py file to improve module imports and organization. The most important changes include adding imports for key classes and functions, and removing an unnecessary import.

Improvements to module imports:

• Added imports for BlinkStick, BlinkStickPro, BlinkStickProMatrix, find_all, find_by_serial, and find_first from the blinkstick module.
• Added imports for Color and ColorFormat from the colors module.
• Added import for BlinkStickVariant from the constants module.
• Added import for BlinkStickException from the exceptions module.

Codebase simplification:

• Removed the import for main from the main module.Improve the discoverability of the key parts of the blinkstick package by exposing them at the top level.