[keymap] add settings-window shortcut

[DaVukovic]

Description

Add a shortcut to enter the Kodi settings

Motivation and context

Some skins provide the option to disable various menu items. One is able to disable the "settings"-button as well to enter the Kodi settings. For what I can tell, disabling the settings-button is mostly not done on purpose. It happens via accident and for some ppl it's somewhat hard to revert this change.

Sure one is able to edit the settings.xml (if they know how the setting is named) or use kodi-send -a "ActivateWindow(Settings) or use the JSON API....but I think this might be way easier

How has this been tested?

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Compiled and tested on Fedora

What is the effect on users?

Users are able to access the settings via a keyboard by pressing alt + s

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[fuzzard]

Seems reasonable

[garbear]

Keyboard shortcut proliferation could be undesirable, but in this case a settings-window shortcut seems needed to recover from some skins.