Add shortcuts to ease navigation

[Perdu]

• Ctrl+End to go to last tab
• Ctrl+Home to go to currently active tab (playing/paused)
• Ctrl+C to close current tab

Notes:

• I used Ctrl-C instead of Ctrl-W because Ctrl-W is already taken by src/core/mainwindow.cpp:1065. However, that does not seem to be doing anything for me (on Arch Linux / i3). I think this deserves investigation. If this is broken/old code, I think that shortcut could be reclaimed for closing tabs.
• Proposed implementation makes Ctrl+Home return to active tab, or to first tab if none is active. This may be confusing for users and could be restricted to not doing anything if no tab is active.

[Perdu]

CI run errors are unrelated to the patch

[jonaski]

CTRL + End and CTRL + Home is already for moving up and down the playlist without selecting the track, so another combination must be used. I also don't like CTRL + C since that's usually copy to clipboard or interrupt program.

CTRL + W works here, it minimizes the window.