Missing important shortcuts

[Geekley]

Some important shortcuts don't work (either non-existent or should be improved).
I also recommend adding a link to https://www.pinta-project.com/user-guide/shortcuts/ in the Help menu for accessibility.

Shortcuts not listed in that page (these would make behavior consistent with tabs in browsers):
- Cycle Tabs (in recent used order): Ctrl+Tab and Ctrl+Shift+Tab
- Go to Left|Right Tab (in listed order): Ctrl+PgUp and Ctrl+PgDown
- Reopen Last Closed Tab: Ctrl+Shift+T - this shortcut is incorrectly listed as Brightness/Contrast
- New Tab (like New... but use same dimensions as current document without asking, I also suggest adding a "plus" button after last tab): Ctrl+T

Listed, but not working for me:
- Go to Layer Above|Below|Top|Bottom:
  Not working, at least in Flatpak version. I also suggest changing them to just PgUp|PgDown|Home|End for efficiency and simplicity.
- Rotate/Zoom Layer:
  It's listed as Ctrl+Shift+Z, which is Redo on Linux. I suggest setting Ctrl+Shift+Z as an alternative to Ctrl+Y for Redo on ALL platforms, and changing this command to some other shortcut.

Listed incorrectly in the page:
- Brightness/Contrast: it's Ctrl+Shift+B for me
- Black and White: it's Ctrl+Shift+G for me

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Version: 1.7/stable (Flathub)
Operating System: Kubuntu 21.04 amd64
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.80.0
Qt Version: 5.15.2
Kernel Version: 5.11.0-38-generic
Graphics Platform: X11

[Geekley (geekley)]

Related: https://communiroo.com/PintaProject/pinta/suggestions/476/make-tabs-more-consistent-with-how-they-behave-in-browsers