Include default command settings in stack config file

[ncoghlan]

There are several locking, build, and publishing settings which could reasonably be considered part of the stack specification:

• package index access settings
• whether to produce tagged or untagged outputs
• where to find additional local wheel archives
• locking mode to use (once #2 has been implemented)
• default locations for working and output artifact directories

While settings these globally or per-user doesn't necessarily make sense (although #20 would allow that to some degree), it does make sense to allow the stack specification file to include a [config] section which changes the default values used for various settings.

https://maxb2.github.io/typer-config/latest/ may be a useful dependency to consider for this purpose (as this idea would be similar to the "pyproject.toml section" approach described in https://maxb2.github.io/typer-config/latest/examples/pyproject/ )

[ncoghlan]

Another good candidate for inclusion as a stack config setting:

• 90