Improve tail line, fix edit box

* Edit box now supports the usual keys; left/right plus home/end, and does
  the appropriate scrolling.
* Tail line is now a top bar.
* Added option to toggle tail bar, but not bound to any key.

src/Settings.php

@@ -14,6 +14,8 @@ class Settings
 
     public static bool $highlightRow = true;
 
+    public static bool $tailLine = true;
+
     public static function load(string $filename): void
     {
         if (file_exists($filename) && is_readable($filename)) {