[Feature Request] Add insertText(text) API to insert plain text at cursor

EnrichedTextInput currently provides formatting commands (bold, image, mention, link, etc.), but there is no API to insert plain text at the current cursor position.

A simple method like:

insertText(text: string): void

would allow developers to implement common features such as inserting emoji (😄), autocomplete suggestions, custom keyboard input, and snippet insertion. Using setValue() is not a solution because it breaks formatting, history, and cursor state.

This feature requires only minimal native changes and would greatly improve integration with custom input components.