add text insertion at cursor position

[s-light]

Todo:

• implement _get_cursor_position()
• implement _buffer_handle_cursor_position()
• implement word-wise movement (Ctrl + arrow left / right)

some references

• https://notes.burke.libbey.me/ansi-escape-codes/
• https://www.lihaoyi.com/post/BuildyourownCommandLinewithANSIescapecodes.html