Allow to include and style legend (key-image) in diagrams

[Kieninger]

Description

As a software engineer using structurizr,
I would like to have the possibility to add a legend to all diagrams (System Context, Container, Component, ...) instead of having an additional "key" image exported,
so that I can easily add my diagrams to some documents (PDF, Word, ...), which don't support structurizr-ui.

Legend styling would be beneficial like changing the size of the boxes or fonts, so that the legend is not that big compared to the actual boxes.

Example:

Priority

I have no budget and there's no rush, please add this feature for free

More information

No response