fix: make dynamic CSS object optional

Author: streamich

addon/drule.d.ts

@@ -1,8 +1,8 @@
-import {CssLikeObject, TDynamicCss} from '../types/common';
+import {CssLikeObject} from '../types/common';
 import {NanoRenderer} from '../types/nano';
 
 export interface DruleAddon {
-    drule: (css: CssLikeObject, block?: string) => TDynamicCss;
+    drule: (css: CssLikeObject, block?: string) => (css?: CssLikeObject) => string;
 }
 
 export function addon(nano: NanoRenderer);