add and bind file loading + api

src/mesh/api.js

@@ -211,6 +211,7 @@ let model = {
     }
 };
 
+// api is augmented in mesh.build
 let api = mesh.api = {
     clear() {
         for (let group of group.list()) {
@@ -245,6 +246,11 @@ let api = mesh.api = {
 
     model,
 
+    import() {
+        // binding created in mesh.build
+        $('import').click();
+    },
+
     objects() {
         // return model objects suitable for finding ray intersections
         return group.list().map(o => o.models).flat().map(o => o.object);