Version 2.3.1

Starting with this release, all npm dependencies of the VSDX Export library are loaded from npmjs.com. This should eliminate any problems that may have occurred during npm install of the dependencies.

Previously, our forks of the canvg and antlr4 libraries were loaded from their respective GitHub repositories. This caused errors for users of npm v7 and newer when installing the canvg dependency. In addition, installation from GitHub could be problematic for users with incorrect git/ssh configurations or from within (corporate) networks with restrictive access policies.