This has been a huge support burden for us. I seriously considered doing
this in 3.0 but caved to a vocal minority and the desire to keep as much
backwards compatibility as possible. At this point, however, I'm done
witnessing the abuse Anthony has to suffer over this and I'm done with
the undue hostility that people who don't bother to read the docs
display. Hopefully, this eases that a bit.

Since Flake8 3.0 we've had the ability for plugins to use
`extend_default_ignore` to register codes they want disabled by default.
This, however, was a permanent disabling unfortunately. Our code didn't
have a way of understanding that this new set of `ignore` codes was
actually the 'default' set for that run. Much like the
extended_select_list, we now attach extended_ignore_list to be able to
confidently determine if the ignore we get in the DecisionEngine is
actually the Default Ignore list and what plugins what us to ignore by
default.

Refs https://github.com/PyCQA/pep8-naming/pull/157

Typo fix