Added TypeScript for frontend

Added type definitions for components, functions, data
Added guards for network responses
fixes #8

front/src/components/index.ts

@@ -0,0 +1,19 @@
+import AnnouncementDetails from "./AnnouncementDetails"
+import BottomNavBar from "./BottomNavBar"
+import Filters from "./Filters"
+import LineDot from "./LineDot"
+import LocationMarker from './LocationMarker'
+import TrashboxMarkers from './TrashboxMarkers'
+import WithToken from './WithToken'
+import ClickHandler from './ClickHandler'
+
+export {
+    AnnouncementDetails,
+    BottomNavBar,
+    Filters,
+    LineDot,
+    LocationMarker,
+    TrashboxMarkers,
+    WithToken,
+    ClickHandler,
+}