Create system to build and upload the docs to sbml.org

[luciansmith]

https://github.com/sbmlteam/sbml-org-website/tree/main/site/static/software/libsbml/ contains the actual source of the latest docs. libsbml should add a new 'build docs' target so the docs are built automatically, and then a note added to the release procedure to remember to upload the latest to that directory.

[luciansmith]

(Tagging this as 'bug' because the 5.19.0 docs don't currently build.)

[fbergmann]

well the thing is no one knows how to build the docs ... we know mike had a system with the gnu make build, but i'm not sure how it worked. so it is definitely a documentation issue .. and and implementation issue, as we need to know what to translate into the cmake build.