feat!: improve saving locations

Shows saved home and work locations with a marker on the map and provides a better API for saved locations opening room for more locations in the future

BREAKING CHANGE: no longer uses saved.home, saved.work localStorage entries, locations need to be re-entered to use the saved entry instead

src/lib/saved.svelte.ts

@@ -0,0 +1,7 @@
+export const saved: Record<string, WorldLocation> = $state(
+	JSON.parse(localStorage.getItem("saved") ?? "{}"),
+);
+
+export function saveLocations() {
+	localStorage.setItem("saved", JSON.stringify(saved));
+}