feat(color-scheme): add color scheme settings

Added an appearance settings section containing a color scheme setting
and translations for that.

src/features/settings/settings.json

@@ -1,3 +1,30 @@
 {
-    "contents": []
+    "contents": [
+        {
+            "name": "appearance",
+            "i18n": "settings.settings.appearance.title",
+            "content": [
+                {
+                    "name": "colorScheme",
+                    "type": "selection",
+                    "i18n": "settings.settings.appearance.contents.colorScheme.title",
+                    "default": "auto",
+                    "options": [
+                        {
+                            "name": "auto",
+                            "i18n": "settings.settings.appearance.contents.colorScheme.options.auto"
+                        },
+                        {
+                            "name": "light",
+                            "i18n": "settings.settings.appearance.contents.colorScheme.options.light"
+                        },
+                        {
+                            "name": "dark",
+                            "i18n": "settings.settings.appearance.contents.colorScheme.options.dark"
+                        }
+                    ]
+                }
+            ]
+        }
+    ]
 }

src/locales/de.json

@@ -60,6 +60,21 @@
             "option": {
                 "ariaLabel": "Wählt die Option {option} aus"
             }
+        },
+        "settings": {
+            "appearance": {
+                "title": "Erscheinungsbild",
+                "contents": {
+                    "colorScheme": {
+                        "title": "Farbschema",
+                        "options": {
+                            "auto": "An Systemfarbschema anpassen",
+                            "light": "Hell",
+                            "dark": "Dunkel"
+                        }
+                    }
+                }
+            }
         }
     }
 }

src/locales/en.json

@@ -60,6 +60,21 @@
             "option": {
                 "ariaLabel": "Selects option {option}"
             }
+        },
+        "settings": {
+            "appearance": {
+                "title": "Appearance",
+                "contents": {
+                    "colorScheme": {
+                        "title": "Color Scheme",
+                        "options": {
+                            "auto": "Adapt to system color scheme",
+                            "light": "Light",
+                            "dark": "Dark"
+                        }
+                    }
+                }
+            }
         }
     }
 }