stub out inital public facing functions.

SmoulderingBeachBall/SmoulderingBeachBall/ImageMaker.fs

@@ -1,5 +1,12 @@
 namespace SmoulderingBeachBall
 
 module ImageMaker =
-    let hello name =
-        printfn "Hello %s" name
+
+    let makeImage width height colour =
+        null
+
+    let addOverlay colour image =
+        null
+
+    let saveImage filePath =
+        null