Collect application resources for #433 (#833)

docs/book/src/dev/commands.md

@@ -9,7 +9,7 @@ parameters and never open dialogs; a dialog is a front-end form that builds the
 ```rust
 CommandSpec::new("solid.fillet", "Fillet", fillet)
     .at("SOLID", "MODIFY")      // toolbar tab and panel ("" = not on the toolbar)
-    .icon("fillet")             // drawn in code, crates/ui-egui/src/icons.rs
+    .icon("fillet")             // drawn in code, assets/icons/ui/source/icons.rs
     .key("F")                   // default shortcut
     .params("edges: [[x,y,z] | {body, index}]; radius: expr; …"),
 ```