view-switcher: Recommend to use a HdyHeaderBar

This will help users of HdyViewSwitcher to know how to make it look
good in a header bar.
7 jobs for header-bar in 9 minutes and 38 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #43811
librem5
build-debian-clang

00:02:44

passed #43809
librem5
build-debian-gcc

00:03:06

passed #43810
librem5
build-debian-gcc-static

00:01:57

passed #43812
librem5
build-fedora-gcc

00:02:27

 
  Docs
passed #43813
librem5
build-gtkdoc

00:01:28

 
  Test
passed #43814
librem5
unit-test

00:02:57

44.4%
 
  Package
passed #43815
librem5
package-debian

00:02:05