Consider adding extra bmad-doc output with examples and regression tests

[ken-lauer]

Comment:

For downstream testing (for pytao and its feedstock, for example), it would be nice if there were a package that included bmad's documentation and regression tests.

• https://github.com/bmad-sim/bmad-ecosystem/tree/main/bmad-doc
• https://github.com/bmad-sim/bmad-ecosystem/tree/main/regression_tests

These are quite large and would be unnecessary for general installations. However, perhaps they could be added as a separate output: https://conda-forge.org/docs/maintainer/knowledge_base/#multi-output-recipes
If included, ACC_ROOT_DIR and relevant bmad environment variables could be set as well to make it seamless.