feat: add basic menu state

game/state/handlers/menu.go

@@ -0,0 +1,28 @@
+package handlers
+
+import (
+	"tetris/engine/render"
+	"tetris/game/state"
+
+	rl "github.com/gen2brain/raylib-go/raylib"
+)
+
+type Menu struct{}
+
+func (menu *Menu) Enter() {
+}
+
+func (menu *Menu) Exit() {
+}
+
+func (menu *Menu) Update(fsm state.Transitioner, delta float32) {
+	if rl.IsKeyPressed(rl.KeyEnter) {
+		fsm.Switch("gameplay")
+	}
+}
+
+func (menu *Menu) Render() {
+	render.Begin(rl.Black)
+	render.DrawText(250, 400, 32, "Start", rl.White)
+	render.End()
+}