change markdown library to markdown-it-python and add Graphviz support

change images to be assets and allow for more file types per #25

add new homepage content update page

update landing page links for links to sourcehut

update footer to include source code link

fix landing page link

update footer to include link to docs site

fix user update form to account for allow_docs_user env variable

update allow for docs user if env variable

fix views where user does not have an rsl record

Initial commit from GitHub