Desktop: Add native file dialogs (#2939)

* Add native open file dialog

* Add native save file dialog

* Fix integer underflow in defer message handler

* Update nix flake

* Cleanup

---------

Co-authored-by: Dennis Kobert <dennis@kobert.dev>

editor/src/messages/frontend/frontend_message.rs

@@ -12,6 +12,7 @@ use graph_craft::document::NodeId;
 use graphene_std::raster::Image;
 use graphene_std::raster::color::Color;
 use graphene_std::text::{Font, TextAlign};
+use std::path::PathBuf;
 
 #[cfg(not(target_family = "wasm"))]
 use crate::messages::portfolio::document::overlays::utility_types::OverlayContext;
@@ -63,6 +64,12 @@ pub enum FrontendMessage {
 		#[serde(rename = "commitDate")]
 		commit_date: String,
 	},
+	TriggerSaveDocument {
+		document_id: DocumentId,
+		name: String,
+		path: Option<PathBuf>,
+		document: String,
+	},
 	TriggerDownloadImage {
 		svg: String,
 		name: String,