Add compability for spatie/eloquent-sortable 4 and add nova dependency (#31)

Author: mstaack

composer.json

@@ -8,7 +8,8 @@
     "license": "MIT",
     "require": {
         "php": ">=7.1.0",
-        "spatie/eloquent-sortable": "^3.4"
+        "laravel/nova": "^2.0|^3.0",
+        "spatie/eloquent-sortable": "^3.4|^4.0"
     },
     "autoload": {
         "psr-4": {