Security - CVE-2021-41184: Upgrade embedded jQuery UI Position to 1.13+ (v2.x)

This plugin embeds jQuery UI Position v1.12 (https://github.com/swisnl/jQuery-contextMenu/blob/master/dist/jquery.ui.position.js). This version of jQuery UI is susceptible to Cross Site Scripting and is officially unsupported by jQuery UI.

Upgrading this embedded code to jQuery UI 1.13 closes these known security vulnerabilities.

CVE: https://www.cve.org/CVERecord?id=CVE-2021-41184 / https://security.snyk.io/vuln/SNYK-JS-JQUERYUI-1767175 jQuery UI: https://jqueryui.com