feat(i18n): add Turkish translation (#15000)

This pull request introduces support for the Turkish language to the
frontend internationalization system and adds a new pull request
template to standardize PR descriptions. The main changes are grouped
below:

**Internationalization: Turkish Language Support**
* Added `'tr'` (Turkish) to the `Language` type and
`SUPPORTED_LANGUAGES` object in `index.ts`, including its display name,
native name, flag emoji, and resource loader.
[[1]](diffhunk://#diff-ba5f665c3490d0f5acb2cb70f08314c5373137fa8085ab05175047f10cb7fdf8L26-R27)
[[2]](diffhunk://#diff-ba5f665c3490d0f5acb2cb70f08314c5373137fa8085ab05175047f10cb7fdf8R183-R188)
* Updated `i18n-completenesses.json` to include Turkish (`"tr": 6`).

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
  * Turkish language can now be selected in the app.

* **Localization**
* Initial Turkish translations added and translation completeness set to
100%.
* Locale metadata added (display name, original name, flag) for Turkish.

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packages/frontend/i18n/src/i18n-completenesses.json

@@ -23,5 +23,6 @@
   "uk": 93,
   "ur": 100,
   "zh-Hans": 97,
-  "zh-Hant": 93
+  "zh-Hant": 93,
+  "tr": 100
 }

packages/frontend/i18n/src/resources/index.ts

@@ -24,7 +24,8 @@ export type Language =
   | 'pt-BR'
   | 'fa'
   | 'nb-NO'
-  | 'kk';
+  | 'kk'
+  | 'tr';
 
 export type LanguageResource = typeof en;
 export const SUPPORTED_LANGUAGES: Record<
@@ -186,4 +187,10 @@ export const SUPPORTED_LANGUAGES: Record<
     flagEmoji: '🇰🇿',
     resource: () => import('./kk.json'),
   },
+  tr: {
+    name: 'Turkish',
+    originalName: 'Türkçe',
+    flagEmoji: '🇹🇷',
+    resource: () => import('./tr.json'),
+  }
 };