[MRG + 1] DOC Add whatsnew for the 3 model_selection bugfixes (#7868)

* DOC Add whatnew for the 3 mod-sel bugfixes

* Move to 0.18.1; Change name universally to Raghav RV

* Raghav R V --> Raghav RV

* Edit mailmap to include my other email

# Conflicts:
#	doc/whats_new.rst