Suggestion: Store URL extensions in project as well

[CST1229]

This has been suggested by 2 separate users in the Discord before.

Sometimes, extensions loaded from URL might go down, or users might, say, have the URL blocked or are using an outdated version of the desktop app (though this wouldn't protect against extension updates). Due to this, maybe extensions loaded from URL could also be stored in the project as well.

The way I would see it work:

• When initially adding the extension, you will need to be able to fetch the URL.
• When loading a project, the URL will first be fetched, and if that fails, it will use the version stored in the project file (if there is any. If there isn't, the project will fail to load).
• When saving, if it could fetch the up-to-date extension from URL, it will save that into the project file (in the same way as file/text extensions), otherwise it will just reuse the stored version again.

One concern about this, though, could be filesize (mostly for extensions that bundle huge libraries).

[AD1340]

very important pls listen to this guys