add text editor example

README.md

@@ -49,6 +49,7 @@ cargo run --example minimal
 
 - [minimal](./examples/minimal.rs): Minimal usage with [crossterm][] support
 - [termion](./examples/termion.rs): Minimal usage with [termion][] support
+- [editor](./examples/editor.rs): Simple text editor to edit multiple files
 
 ## Minimal Usage
 
@@ -473,6 +474,8 @@ loop {
 }
 ```
 
+See [`editor` example](./examples/editor.rs) for working example.
+
 ## Contributing to tui-textarea
 
 This project is developed [on GitHub][repo].