Add XML documentation for Android.Net.Wifi.P2p.Nsd

The `Android.Net.Wifi.P2p.Nsd` namespace contains **92** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

Example command:

```powershell
rg -n -i --glob 'Android.Net.Wifi.P2p.Nsd/**' --glob 'ns-Android.Net.Wifi.P2p.Nsd.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **84** to **92** (increased by **8**). Related documentation PRs: [#644](https://github.com/dotnet/android-api-docs/pull/644).

Start with the XML files under docs\xml\Android.Net.Wifi.P2p.Nsd and the ns-Android.Net.Wifi.P2p.Nsd.xml file. Run the provided rg command to locate all 92 "To be added" placeholders, then review the surrounding API entries and replace the placeholders with documentation. Done means the namespace scan finds no remaining placeholders, excluding docs\xml\index.xml.

Written by the indexing model from the issue text.