Add a smiling emoji example using different shapes (#124)

examples/dune

@@ -122,3 +122,9 @@
  (name fill_rect)
  (modules fill_rect)
  (libraries joy))
+
+(executable
+ (name smile)
+ (modules smile)
+ (libraries joy))
+

examples/smile.ml

@@ -0,0 +1,27 @@
+open Joy
+
+let make_nose () =
+    let l = line (point 0 50)|> translate 0 (-25) in
+    let l1 = l in
+    let l2 = l |> rotate 90|> translate 0 (-25) in
+    let nose = complex [l1; l2] in
+    nose
+
+let make_arc rx ry = 
+    let r = rectangle ~c:(point 0 (ry / 2)) (2 * rx) ry in 
+    let col = r |> with_fill white |> with_stroke white in
+    let e = ellipse ~c:(point 0 0) rx ry in
+    complex [e; col]
+
+let () =
+    init ();
+    let a = circle 200 in
+    let d = circle ~c:(point 50 50) 20 in
+    let b = circle ~c:(point (-50) 50) 20 in
+    let nose = make_nose () in
+    let leb = make_arc 26 14 |> rotate 180 |> translate 50 70  in
+    let reb = make_arc 26 14 |> rotate 180 |> translate (-50) 70  in 
+    let mouth = make_arc 80 40 |>translate 0 (-60) in 
+    show [mouth;leb;reb;a;d;b;nose];
+    write ()
+