de/Adjust weekday indexing to match standard convention in date_time.json

There is a potential issue in ovos_date_parser/res/de-de/date_time.json where the weekday indexing starts from Monday (0) instead of the standard convention where Sunday is 0. This might cause compatibility issues with datetime libraries.

Adjust weekday indexing to match standard convention.

The current indexing (Monday = 0) differs from the standard convention where Sunday = 0. This might cause compatibility issues with datetime libraries.

   "weekday": {
-    "0": "Montag",
-    "1": "Dienstag",
-    "2": "Mittwoch",
-    "3": "Donnerstag",
-    "4": "Freitag",
-    "5": "Samstag",
-    "6": "Sonntag"
+    "0": "Sonntag",
+    "1": "Montag",
+    "2": "Dienstag",
+    "3": "Mittwoch",
+    "4": "Donnerstag",
+    "5": "Freitag",
+    "6": "Samstag"
   },

Referenced in PR: https://github.com/OpenVoiceOS/ovos-date-parser/pull/1
Comment URL: https://github.com/OpenVoiceOS/ovos-date-parser/pull/1#discussion_r1831942344

Reported by @JarbasAl.