Ability to copy over shortcuts from preference pack to current theme

**Is your feature request related to a problem? Please describe.**
Preference Packs provide the ability to customize the FreeCAD UI in a multitude of ways. But there exists a scenario where a user might already like the esthetic UI/UX setup they want but want to import just keyboard shortcuts from another Preference Pack. This feature would provide a way to solely import a Preference Pack's assigned keyboard shortcuts (nothing else)

**Describe the solution you'd like**
In the Preferences of the Preference Pack menu clicking on the a specific Preference pack opens up a confirmation dialog asking if the user is sure they want to install chosen pref pack. In this dialog create a checkbox that when enabled solely imports said pref pack's keyboard shortcuts.

**Describe alternatives you've considered**
A macro that pulls shortcuts from prefpacks and implements them in the user's user.cfg. Or manually opening up a pref pack and copy/pasting (xml) shortcuts in to one's own `user.cfg`

**Additional context**
Forum mention: https://forum.freecadweb.org/viewtopic.php?style=1&p=574337#p574337