nomnoml is a website that allows you to specify complex diagrams without drawing them. It can make flow charts as well as UML diagrams.

nomnoml exports Server-hosted SVG, which is basically using a web-friendly string of the coding that you can type in.
I have implemented an encoding of the text in a Code Block that is replaced by the rendered diagram.

This is a very powerful method where you are supporting technical documentation.

Do use the nomnoml website directly for larger projects as the downloaded SVG contains it own Code definition, making it easy to re-edit at any time.

JS - nomnoml UML Diagramming.xar