Added TypeScript for frontend

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

front/src/hooks/api/useTrashboxes.ts

@@ -0,0 +1,35 @@
+import { LatLng } from "leaflet"
+
+import { API_URL } from "../../config"
+import { isArrayOf, isObject } from "../../utils/types"
+import useFetch from "./useFetch"
+import { isString } from "../../utils/types"
+
+type Trashbox = {
+    Lat: number,
+    Lng: number,
+    Address: string,
+    Categories: string[]
+}
+
+const isTrashbox = (obj: unknown): obj is Trashbox => isObject(obj, {
+    "Lat": "number",
+    "Lng": "number",
+    "Address": "string",
+    "Categories": obj => isArrayOf<string>(obj, isString)
+})
+
+const useTrashboxes = (position: LatLng) => {
+    return useFetch(
+        API_URL + "/trashbox?" + new URLSearchParams({
+            lat: position.lat.toString(),
+            lng: position.lng.toString()
+        }).toString(),
+        undefined,
+        [],
+        (obj): obj is Trashbox[] => isArrayOf(obj, isTrashbox)
+    )
+}
+
+export type { Trashbox }
+export default useTrashboxes