Make it possible to directly load the script into a page

[Weasy666]

Please provide a markdown-it-plantuml.js file that can be directly loaded into a page.
As an example you could look at how markdown-it-footnote does it.

They provide a script file that adds itself as a module globally, so that it can be called with window.markdownitFootnote. This would be really great and enable the use of PlantUML in BookStack.