Add Ski Area favorite functionality backed by local storage

[maxmchu]

Product changes

• This PR adds the ability to add favorite Ski Areas to OpenSkiMap. Favorites are stored locally in the browser.
• Favorites are displayed in the Sidebar below the Privacy / Cookie Policy links, and ordered in reverse chronological order of when they were added.
  
• Favorites can be added by tapping on the Heart icon in the bottom right corner of the Info Card.
  
• Tapping on a Favorite Ski Area in the sidebar will pan the map to that Ski Area and open the Info Card.
  
• Favorites can be removed by tapping on the Heart icon on the associated info card.

Video demo

compress.mov

In this video, we do the following:

• Start with a fresh map with no favorites added.
• We add some favorite ski resorts
• We tap on the favorites and pan around the map
• We refresh the page, showing that the favorites persist
• We remove a favorite and verify it no longer shows in the sidebar

Technical details

• Add a FeatureFavoriteService managing local storage of Favorite Features -- this service is capable of handling favoriting Runs + Lifts, but I personally find that Ski Areas is probably the most helpful.
• Local storage stores a Map of IDs to metadata objects that store the ID, the feature type, and when the favorite was added. The feature information is fetched when opening the Sidebar.
• Add a FeatureFavorites component that is embedded into the Sidebar component to render ListItems/Buttons
• Add a FeatureFavoriteControl component that is embedded into the SkiAreaInfo component in the bottom-right corner by adding it as an Action

[maxmchu]

Added a commit to add tooltip explanation messages: