title: indexeddb get all keys from object store
body: <p>I'm new to indexeddb.
  Let's say I put several objects to indexed db:</p>
  
  <pre><code>transaction.objectStore("some_store").put(some_object, some_key);
  </code></pre>
  
  <p>Now I want to get all keys from that object store. Is that possible? If yes, how?</p>