fix(elasticsearch-plugin): Fix type to allow the promise on custom ma…

…pping definition (#2562)

packages/elasticsearch-plugin/src/types.ts

@@ -271,7 +271,7 @@ type GraphQlPermittedReturnType = PrimitiveTypeVariations<GraphQlPrimitive>;
 type CustomMappingDefinition<Args extends any[], T extends GraphQlPermittedReturnType, R> = {
     graphQlType: T;
     public?: boolean;
-    valueFn: (...args: Args) => R;
+    valueFn: (...args: Args) => Promise<R> | R;
 };
 
 type TypeVariationMap<GqlType extends GraphQlPrimitive, TsType> = {