This application uses importmap feature, more info about browser support can be found here https://caniuse.com/import-maps.
The information about the feature, which is in proposal state can be seen here https://github.com/WICG/import-maps
If you are using Chrome & Edge, it should work fine, unless your version is older than 89
If you are using Safari, the status of the implementation can be tracked here https://bugs.webkit.org/show_bug.cgi?id=220823
If you are using Firefox, the status of the implementation can be tracked here https://bugzilla.mozilla.org/show_bug.cgi?id=1688879