* Update headers/etc. of older packaging PEPs to reflect replacement PEPs
* Infra: Fix lowercase and tweak plural in text for PyPA spec banner
* Add banner to all relevant PEPs pointing to their canonical PyPA specs
Co-authored-by: Brett Cannon <brett@python.org>
* PEP 1, 12: Update outdated references to Docutils to point to Sphinx
* PEP 1, 12: Update and simplify outdated legacy rendering workflow steps
* Readme: Fix minor issues introduced in PR #2399
* Infra: Update contents to include PEP rendering docs and avoid warnings
* Lint: Update hardcoded PEP link checker to detect new PEP URLs