Add an update button

[sci-comp]

Let's remove the ability to install this as a submodule, and instead include an update button in the dock. This will allow us to delete the weird recursive sub-directories needed to support download from the Godot Asset Library.

[sci-comp]

I'm not in a huge hurry to implement this because I really like having this as a sub-module, hah

[TranquilMarmot]

If you need some inspiration here, phantom-camera has a really nice built-in updater:

https://github.com/ramokz/phantom-camera/tree/main/addons/phantom_camera/scripts/panel/updater

I can't believe Godot still doesn't have a built-in add-on updater; maybe it's coming later as part of the work on the asset store

[sci-comp]

If you need some inspiration here, phantom-camera has a really nice built-in updater:

https://github.com/ramokz/phantom-camera/tree/main/addons/phantom_camera/scripts/panel/updater

I can't believe Godot still doesn't have a built-in add-on updater; maybe it's coming later as part of the work on the asset store

It doesn't really make any sense to me either, which is why I've been procrastinating this task. I don't really want to embed update methods in all the assets I make, but it seems to be how Godot means for us to do things.

I install this as a submodule myself, which is something that I guess shouldn't be supported (you can see the weird dynamic base path nonsense that this causes in the plug-in script).

The developer of GodotSteam said that the new asset store does intend to take the place of the asset library, but he wasn't aware of any possible implementation changes