[3.15] gh-83156: Add dedicated anchor for regexp syntax elements (GH-17470) (#160606)

Co-authored-by: Baptiste Mispelon <bmispelon@gmail.com>
Co-authored-by: Muse Code (Meta Muse Spark)
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Lukasz Langa <ambv@meta.com>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>

Author: 5 people