Async-tkinter-loop

- `AsyncTkLoop` class replaced with functions;
- added documentation strings to functions.

**Full Changelog**: https://github.com/insolor/async-tkinter-loop/compare/0.6.0...0.7.0

- `.destroy()` method of the main window now kills the application (but `.quit()` doesn't);
- fixed a couple of `DeprectionWarning`s in the examples and the `async_tkinter_loop.py` itself.

**Full Changelog**: https://github.com/insolor/async-tkinter-loop/compare/0.5.0...0.6.0

- Type annotations are improved
- The package converted into a single module
- `async_handle` converted into a proper decorator
- Code style improvements

**Full Changelog**: https://github.com/insolor/async-tkinter-loop/compare/0.3.0...0.5.0

- Bump Pillow dependency version to 9.0.1 because of vulnerabilities
- Drop Python 3.6 support
- Use `asyncio.create_task()` instead of deprecated `asyncio.ensure_task()`

- Improved handling of the application closing (avoid using `.protocol("WM_DELETE_WINDOW", ...)` to not interfere with the user's code)
- Unified two separate wrapper functions (`async_command` and `async_event_handler`) into a single `async_handler` function
- Added examples, tests and documentation on usage of the `async_handler` as a decorator
- Last release with Python 3.6 support

The first release which is available on pypi.org (https://pypi.org/project/async-tkinter-loop/0.1.0/)