Configuration idea

[henryiii]

I was thinking, what if we added some options into tool.validate-pyproject? Here's an example of all the options I could come up with, though initially I was thinking about #221:

[tool.validate-pyproject]
check.classifiers = true  #221
check.files = false       #89
enable = []               # List of plugins to enable, empty for all available
disable = []              # List of plugins to ignore 

This would allow us to add default-off checks (example files, above, #89) and default-on (or auto) checks (classifiers) above. enable/disable would address #174 We could also make these CLI options and/or environment variables. I've done similar things for scikit-build-core (toml, env, and config-settings), cibuildwheel (toml and env), and repo-review (toml only). Thoughts?