Use docker image with markdown packaged
Use docker image with markdown packaged

* .github/workflows/main.yml (jobs):
[container]: Use image that is on python3-genenetwork "ad741c1" which
has python-markdown packaged.

genenetwork/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,genenetwork/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2