[QuickAccent]Add support for Serbian Cyrillic (#35500)

* **Languages.cs**
  - Add `GetDefaultLetterKeySRCyrillic` method for Serbian Cyrillic letters.
  - Add `SR_CYRL` entry to `Language` enum.
  - Update `GetDefaultLetterKey` method to include `Language.SR_CYRL`.

* **PowerAccentPage.xaml**
  - Add `ComboBoxItem` for Serbian Cyrillic in `SelectedLanguage` `ComboBox`.

* **Resources.resw**
  - Add entry for Serbian Cyrillic.

* **PowerAccentViewModel.cs**
  - Add `SR_CYRL` to the list of supported languages.

src/modules/poweraccent/PowerAccent.Core/Languages.cs

@@ -47,6 +47,7 @@ namespace PowerAccent.Core
         SL,
         SP,
         SR,
+        SR_CYRL,
         SV,
         TK,
     }
@@ -94,6 +95,7 @@ namespace PowerAccent.Core
                 Language.SL => GetDefaultLetterKeySL(letter), // Slovenian
                 Language.SP => GetDefaultLetterKeySP(letter), // Spain
                 Language.SR => GetDefaultLetterKeySR(letter), // Serbian
+                Language.SR_CYRL => GetDefaultLetterKeySRCyrillic(letter), // Serbian Cyrillic
                 Language.SV => GetDefaultLetterKeySV(letter), // Swedish
                 Language.TK => GetDefaultLetterKeyTK(letter), // Turkish
                 _ => throw new ArgumentException("The language {0} is not known in this context", lang.ToString()),
@@ -144,6 +146,7 @@ namespace PowerAccent.Core
                 .Union(GetDefaultLetterKeySL(letter))
                 .Union(GetDefaultLetterKeySP(letter))
                 .Union(GetDefaultLetterKeySR(letter))
+                .Union(GetDefaultLetterKeySRCyrillic(letter))
                 .Union(GetDefaultLetterKeySV(letter))
                 .Union(GetDefaultLetterKeyTK(letter))
                 .Union(GetDefaultLetterKeyAllLanguagesOnly(letter))
@@ -771,6 +774,19 @@ namespace PowerAccent.Core
             };
         }
 
+        // Serbian Cyrillic
+        private static string[] GetDefaultLetterKeySRCyrillic(LetterKey letter)
+        {
+            return letter switch
+            {
+                LetterKey.VK_D => new[] { "ђ", "џ" },
+                LetterKey.VK_L => new[] { "љ" },
+                LetterKey.VK_N => new[] { "њ" },
+                LetterKey.VK_C => new[] { "ћ" },
+                _ => Array.Empty<string>(),
+            };
+        }
+
         // Macedonian
         private static string[] GetDefaultLetterKeyMK(LetterKey letter)
         {

src/settings-ui/Settings.UI/SettingsXAML/Views/PowerAccentPage.xaml

@@ -1,4 +1,4 @@
-<Page
+<Page
     x:Class="Microsoft.PowerToys.Settings.UI.Views.PowerAccentPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
@@ -88,6 +88,7 @@
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Slovenian" />
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Spanish" />
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Serbian" />
+                            <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Serbian_Cyrillic" />
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Swedish" />
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Turkish" />
                             <ComboBoxItem x:Uid="QuickAccent_SelectedLanguage_Welsh" />

src/settings-ui/Settings.UI/Strings/en-us/Resources.resw

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <root>
   <!-- 
     Microsoft ResX Schema 
@@ -3648,6 +3648,9 @@ Activate by holding the key for the character you want to add an accent to, then
   <data name="QuickAccent_SelectedLanguage_Serbian.Content" xml:space="preserve">
     <value>Serbian</value>
   </data>
+  <data name="QuickAccent_SelectedLanguage_Serbian_Cyrillic.Content" xml:space="preserve">
+    <value>Serbian Cyrillic</value>
+  </data>
   <data name="QuickAccent_SelectedLanguage_Hungarian.Content" xml:space="preserve">
     <value>Hungarian</value>
   </data>

src/settings-ui/Settings.UI/ViewModels/PowerAccentViewModel.cs

@@ -60,6 +60,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
             "SL",
             "SP",
             "SR",
+            "SR_CYRL",
             "SV",
             "TK",
             "CY",