NLWeb 対応

### 概要(Overview)

以下のプロトコルに対応する
https://github.com/microsoft/NLWeb

Shopify では実証済みらしい

### 期待する内容(Expect) or 要望(Requirement)

NLWeb を標準状態で利用できること

The issue names the NLWeb protocol but provides no files, tests, or entry points. Start by determining where protocol integrations belong and what “available by default” means for this PHP application. Done should mean that the expected NLWeb behavior is supported in the standard installation, with acceptance tests identified for the integration.

Written by the indexing model from the issue text.