Add basic installation instructions for QP solvers to the docs

[jfoldi81]

I'm trying to run com.cooperative_tradeoff on a community using some sbml files but cannot because I'm using the default GLPK and don't know how to use IBM Cplex instead. I downloaded it as an academic edition but do not know how to set it as the solver for micom. Thanks in advance!

[cdiener]

The following section from the q2-micom docs may be helpful: https://micom-dev.github.io/q2-micom/#install-a-qp-solver .

[jfoldi81]

Thank you so much! I hadn't seen that page before and now have it working.

[cdiener]

Awesome. I'll add those instructions to the micom docs as well.

[cdiener]

closing in favour of #43