Discover exploration

In this MR I've added a bunch of exploratory features relating to the map / discovery page

• CustomMapStyle.json: used a google tool to generate a map style
• CustomMarker: cache marker prettifying w icons and background colors
• reverse geocoding API test in DevModal
• moved map component out of DiscoverScreen into its own component DiscoverMap
• map camera comes in at an angle
• GeoSearchbar: uses google places autocomplete API to generate location suggestions for searchbar input. doesn't do anything right now other than show results
• navigation: moved away from bottom tab bar. main screen is Discover with buttons to access saved screen and create screen. still needs some styling work
• added temp function to DiscoverScreen to locally generate caches on the map close to a given location