Update second half of Chapter Five, "Command and Menu Reference", in kmail2 documentation.

Add many new items, delete obsolete material, add eight new images.
2 jobs for master in 28 minutes and 12 seconds (queued for 89 minutes and 11 seconds)
Status Name Job ID Coverage
  Build
passed build_clazy_clang_tidy #99599

00:16:11

passed linux kf5-qt5 qt5.15 #99598

00:12:01

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