[Applets] Add initial stuff

include/applets/mii_selector.hpp

@@ -0,0 +1,8 @@
+#include "applets/applet.hpp"
+
+class MiiSelectorApplet final : public AppletBase {
+	virtual Result::HorizonResult start() override;
+	virtual void reset() override;
+
+	MiiSelectorApplet(Memory& memory) : AppletBase(memory) {}
+};