Add method for fetching all weather data sources from IPMD

ipmd/static/ipmd/js/ipmdlib.js

@@ -46,6 +46,12 @@ async function getWeatherDatasource(weatherDatasourceId)
     return await response.json();
 }
 
+async function getWeatherDatasources()
+{
+    const response = await fetch(ipmdWeatherApiURL + "rest/weatherdatasource/");
+    return await response.json();
+}
+
 function getWeatherStationList(weatherDatasource){
     geoJson = JSON.parse(weatherDatasource.spatial.geoJSON);
     let stationList = [];