add a scanw example

example/scanw.nim

@@ -0,0 +1,17 @@
+# a scanw example
+# reference: http://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/scanw.html
+
+import ../ncurses
+
+var 
+    mesg = "Enter a string: "
+    row: cint
+    col: cint
+
+let pwin = initscr()
+getmaxyx(pwin, row, col)
+mvprintw(row div 2, (cint)((col - mesg.len) div 2), "%s", mesg)
+getstr(mesg)
+mvprintw(row - 2, 0, "You Entered: %s", mesg)
+getch()
+endwin()