Add tasks for all the new languages

Task/Factorial/MyrtleScript/factorial.myrtle

@@ -0,0 +1,7 @@
+func factorial args: int a : returns: int {
+    int factorial = a
+    repeat int i = (a - 1) : i == 0 : i-- {
+        factorial *= i
+    }
+    return factorial
+}