Add XML documentation for Android.Text.Style

The `Android.Text.Style` namespace contains **1,034** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

```powershell
rg -n -i --glob 'Android.Text.Style/**' --glob 'ns-Android.Text.Style.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **975** to **1,034** (increased by **59**). Related documentation PRs: [#483](https://github.com/dotnet/android-api-docs/pull/483), [#534](https://github.com/dotnet/android-api-docs/pull/534), [#644](https://github.com/dotnet/android-api-docs/pull/644).

Run the documented rg scan against docs\xml, reviewing the Android.Text.Style/** files and ns-Android.Text.Style.xml while excluding docs\xml\index.xml. Start with the matching placeholder entries and their surrounding API declarations. Done means the 1,034 reported “To be added” placeholders in this namespace have XML documentation and the scan no longer reports them.

Rédigé par le modèle d'indexation à partir du texte de l'issue.