Revert "remove type on ModelField"

This reverts commit fb26e64f.

src/decorators.ts

@@ -8,7 +8,7 @@ export class ModelDecorators<Tables = any> {
     Metadata.set('ModelTableName', name);
 
   ModelField =
-    (def?: ModelFieldDef): PropertyDecorator =>
+    <T = any>(def?: ModelFieldDef<T>): PropertyDecorator =>
     (obj, key) =>
       Metadata.set(
         'ModelField',