Optimize TextString rendering to support browser/OS text features, eg fix native spellcheck (#4733)
Optimize TextString rendering to support browser/OS text features, eg fix native spellcheck (#4733)

* slate-react: use a layout effect to render leaf text nodes instead of via virtual DOM, which implements diffing with real DOM avoiding interference with native TextNode behaviors for example spellcheck

* lint

* clarify and simplify extreme case of null text in TextString rendering

* code style: use string interpolation in TextString

Co-authored-by: Nemanja Tosic <e35931f8d1d16c77ea3a0e3e5292c188692d34b7@gmail.com>

Co-authored-by: Peter Sipos <1a57e9a578f766061ad363b6cf5843c17c31a8e0@craft.do>
Co-authored-by: Nemanja Tosic <e35931f8d1d16c77ea3a0e3e5292c188692d34b7@gmail.com>
ianstormtaylor/slate,ianstormtaylor/slate