doc: sample: add for and while loop samples

doc/sample/WhileLoop.im

@@ -0,0 +1,13 @@
+i = 0.
+sum = 0.
+
+while i < 10 do
+    x = 2.
+    if x == 0 then
+        continue
+    else
+        x += 1
+    end
+end
+
+cout put:"done"