title: add timestamp to pdf with itext MakeSignature.signDeferred
body: <p>I'm using itext MakeSignature.signDeferred to add signature to pdf.
  I use deferred signig because i use external signature container.
  How is possible to add timestamp in this case, the method not support tsaclient parameter like signDetached
     MakeSignature.signDetached(sap, externalDigest, externalSignature, chain, crlList, ocspClient, <strong>tsaClient</strong>, estimatedSize, sigtype);</p>