DNS prefetch control header for Express
=======================================
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This middleware lets you set the `X-DNS-Prefetch-Control` to control browsers' DNS prefetching. Read more about it [on MDN](https://developer.mozilla.org/en-US/docs/Web/HTTP/Controlling_DNS_prefetching) and [on Chromium's docs](https://dev.chromium.org/developers/design-documents/dns-prefetching).

Usage:

```js
const dnsPrefetchControl = require('dns-prefetch-control')

// Set X-DNS-Prefetch-Control: off
app.use(dnsPrefetchControl())

// Set X-DNS-Prefetch-Control: off
app.use(dnsPrefetchControl({ allow: false }))

// Set X-DNS-Prefetch-Control: on
app.use(dnsPrefetchControl({ allow: true }))
```