KHamburgerMenu layout proposal

The following discussion from !51 (merged) should be addressed:

• @felixernst started a discussion: (+4 comments)

  @teams/vdg: I feel like if we want to hide the menu bar by default we need a well thought-out list of actions for the hamburger menu first. Unfortunately I don't really know which that would be because I have only ever used Gwenview on the most basic level.

  It would be great if someone (or we collectively) could figure out what should go into the hamburger menu. I volunteer to implement that proposal.

  For inspiration you might want to have a look at system/dolphin!168 (merged).

Proposal

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And then I think we should put "Rating" in the sidebar's "Operations" tab.