[nostalgia] Make core::init take FileSystem and return Context, add core::setWindowTitle

src/nostalgia/core/gba/gfx.cpp

@@ -100,6 +100,9 @@ ox::Error shutdownGfx(Context*) noexcept {
 	return OxError(0);
 }
 
+void setWindowTitle(Context*, const char*) noexcept {
+}
+
 int getScreenWidth(Context*) noexcept {
 	return 240;
 }