chore: add jspdf-yworks dependency, which is a hidden dependency of svg2pdf right now.

unfortunately, using svg2pdf requires you to use and import jspdf yourself,
and importing svg2pdf and jspdf without require doesn't work well either.

Also, jspdf displays a warning in console every time during imports,
because it's imported twice (once by svg2pdf).
I created an issue and pull request at jspdf-yworks.

package.json

@@ -52,6 +52,7 @@
     "es6-promise": "^4.2.5",
     "jszip": "^3.0.0",
     "loglevel": "^1.5.0",
+    "jspdf-yworks": "^2.1.1",
     "svg2pdf.js": "^1.5.0",
     "typescript-collections": "^1.1.2",
     "vexflow": "^1.2.89"