fix: resolve TS errors without deprecated tsconfig options

Co-authored-by: Cursor <[email protected]>

src/drop/drop.ts

@@ -1,6 +1,7 @@
 import { Context } from '../context'
 
 export abstract class Drop {
+  [key: string]: any
   public liquidMethodMissing (key: string | number, context: Context): Promise<any> | any {
     return undefined
   }