Add support for Kirby 4

Closes #24

Author: lukasbestle

composer.json

@@ -4,7 +4,7 @@
 	"type": "kirby-plugin",
 	"license": "MIT",
 	"homepage": "https://getkirby.com/plugins/getkirby/staticache",
-	"version": "1.0.1",
+	"version": "1.0.2",
 	"authors": [
 		{
 			"name": "Bastian Allgeier",
@@ -18,7 +18,7 @@
 		}
 	],
 	"require": {
-		"getkirby/cms": "^3.8",
+		"getkirby/cms": "^3.8 || ^4.0",
 		"getkirby/composer-installer": "^1.2"
 	},
 	"extra": {