[app] Add hasDivider prop for PageContentSection

[ricoberger]

The PageContentSection component has now a "hasDivider" property to
explicit enable and disable the Divider component. This allows us to
also show an diver when no toolbar is set. Before this the divider was
only enabled when also a toolbar was provided.

• I added a CHANGELOG entry for this change.
• I adjusted the corresponding documentation for this change.
• I adjusted the values.yaml file and the documentation for all values.

[codecov-commenter]

Codecov Report

Merging #372 (ed4e671) into main (5d0a42a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #372   +/-   ##
=======================================
  Coverage   45.40%   45.40%           
=======================================
  Files         132      132           
  Lines       10284    10284           
=======================================
  Hits         4669     4669           
  Misses       5538     5538           
  Partials       77       77           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5d0a42a...ed4e671. Read the comment docs.