Add screenshots from Draw.io to mkdocs

[MerrimanInd]

It would be helpful to have screenshots from Draw.io showing the effects of various formatting choices.

[kinow]

Left a comment on reddit and was going to mention the screenshots, but saw you already had an issue for that. So my +1 here :)

[MerrimanInd]

Added images for all Edge styling options, more to come.

https://merrimanind.github.io/drawpyo/usage/edges/

[kinow]

The images are looking great! Thanks @MerrimanInd !