feat: save body and occurrence visibility with the design (#531) (#592)

Hidden bodies, occurrence placements, sketches and origin items are saved with the design and come back when it is reopened. Visibility is still not an undo step, but hiding or showing something now counts as an unsaved change. Additive field under format 16. Fixes #531.

Co-authored-by: jonaswre <jonas.wrede@beyondit.gmbh>

apps/solidcraft-web/src/main.rs

@@ -110,7 +110,7 @@ mod web {
                 let changed = s.is_dirty() && self.autosaved != Some(s.revision);
                 let wait = AUTOSAVE_S - (now - self.autosaved_at);
                 if changed && wait <= 0.0 {
-                    files::autosave(&self.files, Some((&s.doc, s.path.as_deref())));
+                    files::autosave(&self.files, Some((&s.design(), s.path.as_deref())));
                     self.autosaved = Some(s.revision);
                     self.autosaved_at = now;
                 } else if changed {