Flatpak PoC packaging

[tinywrkb]

This looks like a fun project so I thought I might just try to see if I can get it to work in a Flatpak.
Also, development seems to have halted so this might help users that miss some of the outdated libs.
I'm not really using the app so I'm not sure how well this is working and at least opening a file dialog doesn't seem to work though I'm not sure if it supposed to.
I had to patch saves.js so it will be in a writable location.

The Flatpak manifest is here.
If you look in the history you'll notice that I use the apply-extra step to incorporate the binary release itself in the package but I switched away from this in order to make the Flatpak bundle work. If someone is considering publishing to Flathub then any of the methods is suitable due to the GPL license.

A Flatpak bundle can be downloaded from here. This is for users who just want to install the app and not looking to build it.

I don't plan to publish to Flathub, anyone who wishes to can use my manifest as a startup point.