Add ability to disable Export to - URL via configuration

[Xandrr]

Is your feature request related to a problem? Please describe.
We need to disable "export URL" function in our local instance of draw.io due security reasons.

Describe the solution you'd like
Add startup parameter to override Editor.enableExportUrl value without code editing.

Describe alternatives you've considered
I should manual edit file in my local repository:
src/main/webapp/js/diagramly/Editor.js
@@ -174,7 +174,7 @@
/**
* Disables the export URL function.
*/
Editor.enableExportUrl = true;
Editor.enableExportUrl = false;

Additional context
Add any other context or screenshots about the feature request here.

[davidjgraph]

Why do you specifically want that disabled and not save as XML, extra->edit diagram, etc?