feat(): add buffer to built-in types array

Author: kamilmysliwiec

lib/factories/definitions.factory.ts

@@ -4,7 +4,7 @@ import * as mongoose from 'mongoose';
 import { PropOptions } from '../decorators';
 import { TypeMetadataStorage } from '../storages/type-metadata.storage';
 
-const BUILT_IN_TYPES: Function[] = [Boolean, Number, String, Map, Date];
+const BUILT_IN_TYPES: Function[] = [Boolean, Number, String, Map, Date, Buffer];
 
 export class DefinitionsFactory {
   static createForClass(target: Type<unknown>): mongoose.SchemaDefinition {