Downloaded models are backed up to time-machine - un-necessarily

[alexbbrown]

DiffusionBee downloads 9Gb of models. These are updated occasionally.

For users backing up their drives (this should be everyone!) this un-necessarily fills the backup with content that can be easily retrieved from the internet.

It's easy to prevent this in code in your app:

NSURL* url = //...
[[tildeDiffusionBeeDownloadsURL setResourceValue:@YES] forKey:NSURLIsExcludedFromBackupKey error:nil];

There's a way to do it on command-line if your app is mainly script based:

tmutil addexclusion ~/.diffusionbee/downloads

[gingerbeardman]

If the models were stored in the recommended directories, such as ~/Library/Caches/ and ~/Library/Application Support/ then they would be automatically excluded from backups.

See #183