More properties and cleanup

src/commonMain/kotlin/nl/astraeus/css/properties/Image.kt

@@ -0,0 +1,13 @@
+package nl.astraeus.css.properties
+
+class Image(
+    value: String
+) : CssProperty(value) {
+
+    companion object {
+        fun url(url: String) = Image("url($url)")
+        fun none() = Image("none")
+        fun initial() = Image("initial")
+        fun inherit() = Image("inherit")
+    }
+}