The `window.nostr` object may be made available by web browsers or extensions and websites or web-apps may make use of it after checking its availability.
That object must define the following methods:
```
async window.nostr.getPublicKey(): string // returns a public key as hex
Delegation can be supported in an extension by allowing the user to create a delegatee identity and storing the information necessary to construct the `delegation` tag, such as the signed token. There is no need for the extension to store the delegator's private key.
When operating with a delegated identity, an extension must return the _delegator's_ public key from the `getPublicKey` method, so that the user may see their normal feed upon login. Additionally, during `signEvent`, the extension must modify the event by inserting the _delegatee's_`pubkey`, append a valid `delegation` tag to the end of the tags list and recalculate the event `id`, prior to signing the event.
The client, upon receiving the returned event, need only check for the presence of a `delegation` tag to determine how to handle the event. The client must accept the `id`, `pubkey`, `sig` and `delegation` tag from the signed delegation event.
