If I'm not misunderstanding you, you want to program a game yourself? As far as I know, Itch doesn't provide any game engine (much less powered by the browser). It only hosts games for you. So you'd have to create your own game with the engine of your choice (RPGM, Unity, Godot, GMS2...) and upload it here. If it has HTML support, people could even play it directly from the browser like this one. Hope that helps!