Add ArkTS language support with .ets extension and HarmonyOS samples

- Add ArkTS as a new programming language with .ets file extension
- Configure syntax highlighting using TextMate grammar from ohosvscode/arkTS
- Add real-world ArkTS samples from HarmonyOS development
- Set language ID using script/update-ids (56341321) and color to #3178c6
- Configure ace_mode as typescript and codemirror_mode as javascript
- Add license information for ArkTS submodule

Author: Groupguanfang

lib/linguist/languages.yml

@@ -413,7 +413,7 @@ ArkTS:
   ace_mode: typescript
   codemirror_mode: javascript
   codemirror_mime_type: application/typescript
-  language_id: 1000001
+  language_id: 56341321
 AsciiDoc:
   type: prose
   color: "#73a0c5"