[Feature Requests] Windows support

[I-love-study]

Hi! It's nice to see a library to show sixel image on terminal. But It seems that it cannot running on Windows.
It seems that because of using termios and select in cellsize.py, which is only supported on Unix. And cellsize are imported in __init__.py. So in windows, it cannot be imported.

Consider that preview version of Windows Terminal have already support sixel few months ago(In Windows Terminal Preview v1.22.2362.0). The stable version of windows terminal will also support it in future. I think it's nice to support it on Windows.

I think the fastest way to make it working on windows is to move from .cellsize import get_size from the head of __init__.py into try block in here. So that char_size can as default in (10, 20)

python-sixel/sixel/__init__.py

Lines 136 to 139 in a51ff70

	try:
	char_width, char_height = get_size()
	except Exception:
	char_width, char_height = (10, 20)

By the way, I try to write Windows Implementation for get_size method.
For the size in char, we can use shutil.get_terminal_size to get in both Windows and Unix. But I have no idea how to get the size in pixels on windows.

[7shi]

FYI: There is a fork that implements similar measures to what you are working on:

https://github.com/sbamboo/python-sixel

[TomasTollemark]

Since Sixel support is now a part of both Windows 10(1809+) and Windows 11 i think it is quite important to fix Windows support in python-sixel.

This has already created a mess where there are now two forks around (https://github.com/sbamboo/python-sixel and https://github.com/jakekyee/python_sixel_windows).

Please include Windows support in python-sixel so a user can just run "pip install sixel" on both Linux and Windows and expect it to work.