Add support for using "tomllib" (in Python's stdlib since 3.11) and "tomli" TOML packages. They are preferred if they are found to be installed. But note that the declared dependency for the "toml" extra nevertheless is the "toml" package. Because it is available for all supported Python versions. So use Python 3.11+ or install "tomli" manually if you want to use the alternate packages.

[patterns]
configmix/**.py = RCS, reST
configmix/**.c = RCS, reST
path:README.txt = reST
path:docs/conf.py =