adjust docs

Author: felixheck

README.md

@@ -120,8 +120,8 @@ Required. Example: `foobar`<br/>
 Defining this option enables the traditional method described in the OAuth2 specification and performs an [introspect][introspect] request.<br/>
 Optional. Example: `1234-bar-4321-foo`<br/>
 
-- `publicKey {string}` – The realm its public key related to the private key used to sign the token.<br/>
-Defining this option enables the offline and non-live validation. The public key has to be in [PEM][pem] format.<br/>
+- `publicKey {string|Buffer|Object}` – The realm its public key related to the private key used to sign the token.<br/>
+Defining this option enables the offline and non-live validation. The public key has to be in [PEM][pem] (`{string|Buffer}`) or [JWK][jwk] (`{Object}`) format. Algorithm has to be `RSA-SHA256` compatible.<br/>
 Optional.
 
 - `entitlement {boolean=true}` – The token should be validated with the entitlement API to enable fine-grained authorization. Enabling this option decelerates the process marginally. Mind that `false` is an invalid value.<br/>