ArkTS support added

[sadicelik]

ArkTS (HarmonyOS / OpenHarmony) language support

Summary

Adds first-class extraction support for ArkTS (.ets), the TypeScript
superset used to build HarmonyOS / OpenHarmony apps. ArkTS's headline feature
is declarative UI — an @Component struct with a build() method that
describes the view tree, plus @State/@Prop/@Link reactive props and
global @Builder/@Extend/@Styles functions. A plain TypeScript grammar
parses these constructs as ERROR nodes, so ArkTS needs its own grammar and
extractor.

Tests

__tests__/extraction.test.ts gains an ArkTS Extraction suite covering:

• Language detection (.ets → arkts, .ts → typescript) and
  isLanguageSupported/getSupportedLanguages.
• @Component struct extracted as a component node with @Entry/@Component
  decorators.
• build() and component methods extracted with qualified names
  (Index::aboutToAppear, Index::load).
• @State/@Prop members extracted as properties with their declared types
  and decorators.
• Intra-component method calls (this.load()) resolved.
• Standard TypeScript constructs (classes, enums, interfaces, type aliases,
  method signatures) still extract.
• Global @Builder functions extracted with signature and decorator.

Build / packaging

The new tree-sitter-arkts.wasm is copied into dist/ by copy-assets like
every other vendored grammar — no other build changes.

Notes

• Grammar source: Million-mo/tree-sitter-arkts v0.1.7 (ABI-15 prebuilt wasm).
• Dynamic-dispatch coverage (state → re-render flow synthesis) for ArkTS's
  reactive runtime is not part of this PR — extraction only.