bpo-24147: Document csv Dialect class defaults. Patch by Brandon Milam

[uniocto]

https://bugs.python.org/issue24147

[iritkatriel]

Change the title of the PR to something like:
bpo-24147: Document csv Dialect class defaults. Patch by Brandon Milam.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[MaxwellDupre]

Doesn't compile:
fix-issue-24147 $…  make -C Doc/ html
make: Entering directory '/home/me/Documents/GitHub/cpython/Doc'
mkdir -p build
Building NEWS from Misc/NEWS.d with blurb
PATH=./venv/bin:$PATH sphinx-build -b html -d build/doctrees -W . build/html
Running Sphinx v4.5.0
loading pickled environment... done
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 487 source files that are out of date
updating environment: 0 added, 447 changed, 2 removed
reading sources... [100%] whatsnew/index
Warning, treated as error:
/home/me/Documents/GitHub/cpython/Doc/c-api/complex.rst:49:Error in declarator or parameters
Error in declarator or parameters
Invalid C declaration: Expected identifier, got user-defined keyword: complex. Remove it from c_extra_keywords to allow it as identifier.
Currently c_extra_keywords is ['alignas', 'alignof', 'bool', 'complex', 'imaginary', 'noreturn', 'static_assert', 'thread_local']. [error at 39]
Py_complex _Py_c_neg(Py_complex complex)
make: *** [Makefile:51: build] Error 2
make: Leaving directory '/home/me/Documents/GitHub/cpython/Doc'

The target is Python 2, would it be possible to re-target on the latest version?
The CSV Doc hasn't changed so still relevant.