I realized that there's already a built-in way to include .puml files from the standard library: https://github.com/plantuml/plantuml-stdlib, using <[LibraryName]/[FileName]> syntax.
This switches out the URL include for the cleaner syntax, and it will work the same as the URL include on any PlantUML diagram generator that's using an official PlantUML version.
I realized that there's already a built-in way to include .puml files from the standard library: https://github.com/plantuml/plantuml-stdlib, using <[LibraryName]/[FileName]> syntax.
This switches out the URL include for the cleaner syntax, and it will work the same as the URL include on any PlantUML diagram generator that's using an official PlantUML version.