added comments and refactored code

lib/services/api.dart

@@ -9,6 +9,7 @@ class Api {
   static const String _rootUrl =
       'https://environment.data.gov.uk/flood-monitoring';
 
+  /// Fetches all stationszt
   static Future<List<FloodStation>> fetchAllStations() async {
     List<FloodStation> stations = [];
     final response = await http.get(Uri.parse('$_rootUrl/id/stations'));
@@ -37,7 +38,6 @@ class Api {
 
   /// [limit] limits the number of entries that are requested from the API and [offset] returns the
   /// list starting from the specified number
-
   static Future<List<FloodStation>> fetchStationsByRange(
       int limit, int offset) async {
     List<FloodStation> stations = [];
@@ -52,6 +52,7 @@ class Api {
     return stations;
   }
 
+  /// Fetches all readings from the station with the specified [stationId] from the last 24h
   static Future<List<Reading>> fetchReadingsFromStation(
       String stationId) async {
     List<Reading> readings = [];