docs for creating a module

[lukemarsden]

one day it would also be nice to have docs for how to add new modules, a bit like

• YOU MUST MAKE THEM DETERMINISTIC - see this for AI/ML, otherwise, just make sure you always return the same output with the same input, don't log timestamps in the output, read from /dev/random, be careful with concurrency, map iteration order in go etc
• get it working in bacalhau first, for example bacalhau docker run --gpu 1 ghcr.io/bacalhau-project/examples/stable-diffusion-gpu:0.0.1 -- python main.py --o ./outputs --p "cod swimming through data"
• then run the above command with --dry-run, then port the resulting yaml to a new module file in https://github.com/bacalhau-project/lilypad/tree/main/src/python/modules and add them to https://github.com/bacalhau-project/lilypad/blob/main/src/python/modicum/Modules.py