XWIKI-19270: Add support for performing the PDF export using a browser running...

XWIKI-19270: Add support for performing the PDF export using a browser running in a Docker container
* Force the 1.0 version of the WebSocket API because we're still supporting Jetty 9.4.x and cdt-java-client seems to be compatible with 1.0 version even if it depends on 1.1