Resolve ApiLink URLs from api-docs symbol index

[viktorkombov]

Summary

Updates ApiLink to resolve TypeDoc links through the generated api-docs symbol index before falling back to legacy URL generation.

This lets MDX authors write simple links like <ApiLink type="CategoryChart" /> without manually specifying package/kind/prefix/suffix details.

Changes

• Added ApiLink index client with caching.
• Resolves symbols from combined index when pkg is omitted.
• Uses package-scoped index when pkg is explicitly provided.
• Resolves kind, package URL, suffix/prefix variation, and member anchors from index data.
• Keeps legacy URL fallback when the index is unavailable.
• Leaves Sass ApiLink behavior unchanged.

Testing

• Link astro-components into docs-template.
• Run docs against a local or staging api-docs index.
• Verify:
  <ApiLink type="CategoryChart" />
<ApiLink type="CategoryChart" member="chartType" />
<ApiLink type="Toolbar" exclude="React,WebComponents" />
• Confirm chart links resolve to igniteui-angular-charts, not igniteui-angular.