Add import model button to toolbar

src/app/App.tsx

@@ -2317,9 +2317,17 @@ export function App({ store, initialStatusMessage }: AppProps) {
             <button className="toolbar__button" type="button" onClick={handleExportJson}>
               Export JSON
             </button>
-            <button className="toolbar__button" type="button" onClick={handleImportButtonClick}>
+            <button className="toolbar__button" type="button" onClick={handleImportJsonButtonClick}>
               Import JSON
             </button>
+            <button
+              className="toolbar__button"
+              type="button"
+              onClick={handleImportModelButtonClick}
+              disabled={!projectAssetStorageReady || projectAssetStorage === null}
+            >
+              Import Model
+            </button>
           </div>
 
           <div className="toolbar__group">