Insert SVG: the file picker opens on SVG files (#1801) (#1827)

* claim: #1801

* Insert SVG: the file picker opens on SVG files (#1801)

Every Open went through one host picker whose filters start with designs, CAD
files and meshes, so Insert SVG (and Insert DXF) in a sketch opened on STEP,
IGES and meshes, and the SVG file had to be found under another filter.

The host's pick_open now takes the extensions the command reads and offers
them as the picker's first, default filter. Insert SVG and Insert DXF pass
their type; every other Open passes none and keeps the list it had. The
browser host ignores them (it shows its own file panel).

---------

Co-authored-by: MateuszSychXpl <[email protected]>

apps/solidcraft-web/src/main.rs

@@ -481,7 +481,7 @@ mod web {
                         let panel = files.clone();
                         let services = Services {
                             // Open shows the browser's files (and the computer's, from there).
-                            pick_open: Some(Box::new(move || {
+                            pick_open: Some(Box::new(move |_: &[&str]| {
                                 panel.panel.set(true);
                                 Box::pin(std::future::ready(None))
                             })),