Feature implemented: ThemeSelector which is a ModelScreen from textual.
It is bind to ctrl+t key to open, and can be closed with escape.

Features:

• basic key binding like j/k to navigate.
• real-time theme preview.
• update theme by pressing enter key and updating config file.

Other changes:

• update docs/usage.md file to include this key bind.
• update readme.md quick usage section.
• add test cases for this screen, and snapshot test as well.