PEP 780: ABI features as environment markers (#4315)

Co-authored-by: Lysandros Nikolaou <[email protected]>
Co-authored-by: Ralf Gommers <[email protected]>
Co-authored-by: Adam Turner <[email protected]>

Author: 4 people

.github/CODEOWNERS

@@ -658,6 +658,7 @@ peps/pep-0776.rst  @hoodmane @ambv
 peps/pep-0777.rst  @warsaw
 # ...
 peps/pep-0779.rst  @Yhg1s @colesbury @mpage
+peps/pep-0780.rst  @lysnikolaou
 # ...
 peps/pep-0789.rst  @njsmith
 # ...