"Update dns-over-https-client.mdx" contribution

[unique-EJ]

Summary

This is a first-time pull request.

I added documentation content to the 1.1.1.1 (DNS Resolver) product to give information on an alternative open-source client option, for Android users to connect to and use this Cloudflare product DNS-over-HTTPS (DoH) encryption service.

Screenshots (optional)

Documentation checklist

Please help me by editing any relevant change logs. This is a first-time pull request.

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The documentation style guide has been adhered to (I believe).

[RebeccaTamachiro]

Hi @unique-EJ 👋 Thanks for your contribution.
I have checked internally and will not be listing this in our docs. If you wish, you can share this and other alternatives with other Cloudflare users via our Community.