The README has the following paragraph, which is out of date and can just be deleted:

The RFC Editor is in the process of changing the canonical input format of Internet-Draft and RFC docuemnts. As part of this process, the ability to create artwork which is not ASCII text is being introduced. This is being done with SVG. However, the full set of SVG does not match with the archival nature of RFCs so a subset of the SVG specification is being defined by the RFC Editor that eliminates many capabilities such as animation. Additionally, there is a requirement that the images have the widest possible usage both by printers, monochrome displays and individuals with visual disabilities. Further information on the process can be found on the RFC Editor at the RFC Editor site.

Both RFC 7996 and draft-7996-bis provide sufficient motivating text.