Documentation for Calibration Pipelines

[costachris]

Calibration pipelines are being developed in ClimaAtmos.jl/calibration/experiments. A standard documentation protocol should be used document these pipelines. These can either go into the broader ClimaAtmos docs or be included as Readme's for each respective calibration experiment.

### Tasks
- [ ] Document GCM-driven calibration pipeline (calibration/experiments/gcm_driven_scm)