As by default Storage security rules requires users to be logged in prior saving any files, navigate to Firebase Console and enable Anonymous sign-in method (it's under Authentication -> Sign-in method tab).

Let's sign-in.

await store.auth.methods.anonymous.signIn();

// check out auth user model if you're curious
// →
// {
//   uid: '....',
//   isAnonymous: true,
//   ...
// }

Let's upload a file

ref ='hello');

await ref.put({
  type: 'string',
  format: 'raw',
  data: `Hey there, I'm file.`,
  contentType: 'text/plain',
  metadata: {}

And get the public url:

ref ='hello');
await ref.load({ url: true })
// → "<app-id><token>"

The same works also for Files and Blobs.

See: Storage API documentation for more information