Register app as .gguf file opener

[psugihara]

CFBundleDocumentTypes CFBundleTypeRole: Viewer LSHandlerRank: Default LSItemContentTypes: [".gguf"]

https://developer.apple.com/documentation/uikit/uiapplicationdelegate/1623112-application

when gguf is opened

• load and set opened gguf as current model
• open new chat

Edit: Rather than this, I want FreeChat to open and load the GGUF as if I had set it in the menu.