begin title screen by adding title screen type

fcore/title/title-type.sml

@@ -0,0 +1,17 @@
+signature TITLE_TYPE =
+sig
+  datatype focus = START_BUTTON
+
+  type title_type = {focus: focus}
+
+  val initial: title_type
+end
+
+structure TitleType :> TITLE_TYPE =
+struct
+  datatype focus = START_BUTTON
+
+  type title_type = {focus: focus}
+
+  val initial = {focus = START_BUTTON}
+end

fcore/title/title-update.sml

@@ -0,0 +1,6 @@
+structure TitleUpdate =
+struct
+  open TitleType
+
+  fun update (titleState, input) = titleState
+end