[FEATURE] Get UML name from fragment instead of default from config

[ThaDaVos]

This feature request is simple, to make more use out of this plugin we need to have access to the uml name inside the overridable methods for example the generator - currently this is not possible because the uml code passed is also without @startuml and @enduml. The name is defined as follows according to the PlantUML spec:

@startuml {NAME}
A -> B
@enduml

It would be amazing to have this name available so it can be used for example to save the image with a proper name

[ThaDaVos]

@gmunguia any eta?

[gmunguia]

I saw you mentioned this is "officially supported by PlantUML itself" (in https://github.com/gmunguia/markdown-it-plantuml/issues/13#issuecomment-481665460). Could you expand what you mean by that? Is this feature reflected in PlantUml documentation?