Ability to save searches

**Is your feature request related to a usage problem (not a bug)? Please describe.**
Sometimes I like to search for videos and playlists on broader topics (e.g.: Countries, Music Genres, Games etc.) and I would like to have a list of these searches.

**Describe the solution you'd like to see implemented**
Probably:
- a menu item called "Searches" or "Search Favorites" (or something that sounds better): This would include the list of searches
- a button on the "Search Results" page to add the search to the list

Unlike a recent history of searches, this would only include handpicked favorites.

**Describe alternatives you've considered**

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**Screenshots**

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**Additional context**

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