Add RFT/HTML support

[StudentWeis]

Is your feature request related to a problem? Please describe.

Currently, ropy only supports plain text clipboard content. When I copy formatted text from applications like web browsers, word processors, or code editors with syntax highlighting, all the formatting (bold, italic, colors, links, etc.) is lost when I paste it back. This is frustrating when I need to preserve the original formatting for documentation, emails, or other content where presentation matters.

Describe the solution you'd want

I would like ropy to support rich text formats (RTF, HTML) in addition to plain text. Specifically:

• Store clipboard content with its original formatting
• Display a preview that shows the formatted text in the clipboard history
• Allow pasting content with formatting preserved
• Optionally provide a toggle to paste as plain text when needed