plainAddPlaceholder utf8 support

[tomasantunes]

I need utf8 support on the placeholders. When I insert a name on the placeholder I get garbled text on the final signature.

Here is the code I'm using:

  let inputBuffer = plainAddPlaceholder({
      pdfBuffer,
      reason: 'Signed Certificate.',
      contactInfo: 'joaosilva@email.com',
      name: 'JOÃO SILVA',
      location: 'Porto',
      signatureLength: totalLength,
  });

Here is how it looks on the signature:

[stale[bot]]

This issue has been automatically marked as stale because it has not had activity in the past 90 days. It will be closed if no further activity occurs. Thank you for your contributions.

[erezschatz]

I don't understand how not following on an issue resolves it because it had no activity. Having the same issue here.

[vbuch]

@erezschatz it doesn't resolve it. It just closes it as obviosly noone is going to contribute to it. If you have the issue, you're morte than welcome to reopen it. Even more if you have a PR that solves it.