Missing DefineOptions.schemaDelimiter property

Added missing property `schemaDelimiter` to `DefineOptions` type.
Also added comments on schema and schemaDelimiter properties.

types/sequelize/index.d.ts

@@ -5233,8 +5233,17 @@ declare namespace sequelize {
          * `this.constructor.prototype.find.apply(this, arguments)`
          */
         classMethods?: Object;
-
+        
+        /**
+         * Change the database schema. PG only feature, but also works with other dialects.
+         */
         schema?: string;
+        
+        
+        /**
+         * Change the database schema delimiter. Defaults to "." on PG but for other dialects can be also changed to "_".
+         */
+        schemaDelimiter?: string;
 
         /**
          * You can also change the database engine, e.g. to MyISAM. InnoDB is the default.