Using and showing always local time

routes/api.js
   - console.log deleted

public/javascripts/global.js
   - made 'params' to const
   - added setNoUTC in main

public/javascripts/showcharts.js
   - added setNiUTC to set global at highcharts

package.json
   - added luxon
     "version": "3.0.4",
     "date": "2023-04-24 18:00 UTC",

public/javascripts/global.js

@@ -3,7 +3,7 @@
 
 import * as map from './map.js'
 import * as dt from './datetime.js'
-import {loadAll, showChart} from './showcharts.js'
+import {loadAll, showChart, setNoUTC} from './showcharts.js'
 import { DateTime } from './luxon.min.js'
 import {setCurrentTab, getCurrentTab, showError, fetchfromserver} from "./chart_utilities.js";
 
@@ -14,7 +14,7 @@ import {setCurrentTab, getCurrentTab, showError, fetchfromserver} from "./chart_
     // END global constants
 
     // global variables
-    let params = {                                  // set defaults
+    const params = {                                  // set defaults
         center: Stuttgart,
         zoom: 10,
         span: 1,
@@ -125,6 +125,8 @@ import {setCurrentTab, getCurrentTab, showError, fetchfromserver} from "./chart_
     // show the map if called w/o any parameter
     // if called with a sensor-ID, show the live chart for this sensor
     async function main() {
+        setNoUTC()                                              // no UTC for HighCharts
+        console.log(Intl.DateTimeFormat().resolvedOptions().timeZone)
         // set correct language
         const currentLang =  localStorage.getItem('curlang')
         if(currentLang === 'en') {