Add new example for python custom QEC codes workflows

[kvmto]

While working on #200, it became evident that a new Python example was needed to demonstrate how to create custom quantum error-correcting (QEC) codes with support for diverse noise models. This example will be especially useful for memory experiments and aligns with the goal of providing consistent, complete documentation and sample usage patterns.

Summary of Changes

• Added a new Python example illustrating the creation of custom QEC codes.
• Add the generation of a H and O from DEM.
• Sample the memory experiment.
• Possibly track code capacity.