Adapt to iPadOS‘keyboard cursor

[superwfox]

Hping that the code app team can adapt the software to the keyboard that comes with iPadOS. The function of long pressing the space and sliding cursor is very practical, especially for users without a physical mouse，which could greatly enhance the typing experience🌹

[bummoblizard]

Native text selection is now supported through Runestone editor. See #169 (comment).