Added database handling of DeepL setting

I18N Commander/DataModel/Database/SettingDeepL.cs

@@ -0,0 +1,9 @@
+namespace DataModel.Database;
+
+public enum SettingDeepL
+{
+    DISABLED,
+    
+    USE_FREE_ACCOUNT,
+    USE_PRO_ACCOUNT,
+}

I18N Commander/DataModel/Database/SettingNames.cs

@@ -0,0 +1,6 @@
+namespace DataModel.Database;
+
+public static class SettingNames
+{
+    public static readonly string DEEPL_MODE = "DeepL Mode";
+}