I was able to install graphviz, the extension, setup a project, and create a hello world diagram pretty easily. Change the source code for the diagram and run the plantUML export command (I did with the vscode extension) and then it will generate a file than you can source control. I could see git hooks being very useful here.
This diagram was created with the source code in this repository
For reference: https://marketplace.visualstudio.com/items?itemName=jebbs.plantuml