feat: add clear input functionality to st_keyup component

[ItsThareesh]

Summary This PR adds a clear input functionality to the st_keyup component, as requested in Issue #42

Changes

• Ensured input field resets and syncs properly on state update
• Clear button appears only when text is entered
• Added color change hover animation for clear button
• Updated function headers and typing annotations to match native Streamlit patterns for better consistency