adding new chapter dowhile to summery

Author: sumn2u

en/SUMMARY.md

@@ -24,6 +24,7 @@
 * [Loops](loops/README.md)
     * [For](loops/for.md)
     * [While](loops/while.md)
+    * [Do...While](loops/dowhile.md)
 * [Functions](functions/README.md)
     * [Declare](functions/declare.md)
     * [Higher order](functions/higher_order.md)