I wanted to ask, but is it possible to make a subscription by putting the games in HTML? A person subscribes to your account and then you can play in the browser only if subscribed to the games proposed by the author, is this possible?
You cannot do things account wise on Itch. Itch is project focused. And you do not subscribe to a project. You can make a payment, if possible, and then the project is in your library as an owned game, allowing you to download the files offered for download.
You could offer a download file with a cheat code as an incentive/bonus item ( or the download version of the web game, that's actually rather common).
There are ways of implementing drm, which might work in a web game. That drm would be able to check, if you have bought a game. But imho most users on Itch will not touch drm games. It is just not a selling argument. It is a sale preventing argument. No one buys a game, because it has drm.
The situation changes, if you offer some kind of online game. Then you would use some kind of log in mechanism, which could check, if the game was bought or is played for free. But that's also not a subscription.
Itch seems to collab with Patreon in some way. Or at least they utilize some api. I would rather they offer subspription services themselves, but there is that. So if you want to have account subscription, you might be able to integrate this somehow. But I do not know, if this would work for a web game, as this just gives download keys, which is the same, as if people would have bought the game. https://itch.io/docs/creators/patreon . Also I do not quite understand how this works for subscriptions, since they talk about campaigns. I suspect they repurposed the Kickstarter system.