Port docker setup and docs from cogent3/iqtree2 into cogent3/cogent3

[khiron]

Port the Dockerfile and entrypoint.sh from cogent3/iqtree2 to cogent3/cogent3 a new docker folder of the repo

Port the README.md from cogent3/iqtree2 to cogent3/c3dev
update dependencies for cogent3

Create a README.md in the docker folder of cogent3/cogent3 to describe using a docker container to run cogent3 in linux as a user