Start work on creating and saving new files

gpui/src/platform/test.rs

@@ -1,6 +1,6 @@
 use crate::ClipboardItem;
 use pathfinder_geometry::vector::Vector2F;
-use std::{any::Any, cell::RefCell, rc::Rc, sync::Arc};
+use std::{any::Any, cell::RefCell, path::Path, rc::Rc, sync::Arc};
 
 struct Platform {
     dispatcher: Arc<dyn super::Dispatcher>,
@@ -77,6 +77,8 @@ impl super::Platform for Platform {
     ) {
     }
 
+    fn prompt_for_new_path(&self, _: &Path, _: Box<dyn FnOnce(Option<std::path::PathBuf>)>) {}
+
     fn write_to_clipboard(&self, item: ClipboardItem) {
         *self.current_clipboard_item.borrow_mut() = Some(item);
     }