add jsPDF setProperties to save method and documentProperties to options

[reliacon-dev]

No description provided.

[reliacon-dev]

This is in lieu of the current workaround (which may be useful to the community to document), which requires the implementer to intercept the pdf to directly apply the jsPDF methods themselves:

import * as html2pdf from 'html2pdf.js';
import jsPDF from 'jspdf';
...
const element = document.getElementById('my-element-id');
const worker = html2pdf();
worker.set({
     // options
})
.from(element)
.outputPdf() // generates the PDF prop which can be intercepted
.then(() => {
  // intercept staged PDF to directly apply jsPDF functions
  const pdf: jsPDF = worker.prop.pdf;
  pdf.setProperties({
    title: 'My PDF',
  });
  return worker.save('my-pdf.pdf');
});