Merge branch 'wip/tintou/doc-fixes' into 'master'

docs: Fix several missing references in the documentation

See merge request GNOME/gtk!1874

diff --cc docs/reference/gtk/gtk4-sections.txt
Simple merge

diff --cc docs/reference/gtk/question_index.xml
Simple merge

diff --cc gtk/gtkaboutdialog.c
Simple merge

diff --cc gtk/gtkappchooserbutton.c
Simple merge

diff --cc gtk/gtkmain.c
Simple merge

diff --cc gtk/gtkmountoperation.c
Simple merge

diff --cc gtk/gtkshow.c
Simple merge

diff --cc gtk/gtktextview.c
Simple merge

diff --cc gtk/gtkwidget.c
Simple merge

diff --cc gtk/gtkwidget.h
Simple merge

diff --cc gtk/gtkwindow.c
Simple merge