feat(theme): add Garnet preset with deep red accents (#1418)

app/src/main/res/values/strings.xml

@@ -365,6 +365,7 @@
     <string name="theme_preset_catppuccin">Catppuccin</string>
     <string name="theme_preset_amoled">AMOLED Black (Dark only)</string>
     <string name="theme_preset_nord">Nord</string>
+    <string name="theme_preset_garnet">Garnet</string>
 
     <!-- Language -->
     <string name="settings_item_language">Language</string>