fix: pass drops directly to filters/tags

src/util/underscore.ts

@@ -1,3 +1,5 @@
+import { Drop } from '../drop/drop'
+
 const toStr = Object.prototype.toString
 
 /*
@@ -31,6 +33,10 @@ export function stringify (value: any): string {
   return String(value)
 }
 
+export function toValue (value: any): any {
+  return value instanceof Drop ? value.valueOf() : value
+}
+
 export function toLiquid (value: any): any {
   if (isFunction(value.toLiquid)) return toLiquid(value.toLiquid())
   return value