fix(types): fixed datetime types for optional argument (#192)

Co-authored-by: Shinigami <chrissi92@hotmail.de>

Author: jared-fraser

src/datatype.ts

@@ -95,7 +95,9 @@ export class Datatype {
    * @method faker.datatype.datetime
    * @param options pass min OR max as number of milliseconds since 1. Jan 1970 UTC
    */
-  datetime(options): Date {
+  datetime(
+    options?: number | { min?: number; max?: number; precision?: number }
+  ): Date {
     if (typeof options === 'number') {
       options = {
         max: options,