Search Keywords (CRUD and Auth)

[rebecca-123]

• When the user isn't signed in, when bookmarks is clicked from the navbar, display a modal telling them to sign in to save search keywords
• Display the user's bookmarked search keywords rather than the hard-coded list
• Allow users to add and remove search keywords
• Allow users to easily search using a saved search keyword

Feel free to change the UI and implement the above functionality how you'd like (doesn't have to be the same as the old ZotNFound)