feat: add dreamhost webook provider to readme

[asymingt]

Description

Add a webhook for proxying DNS record updates to the Dreamhost HTTP API per these instructions:
https://help.dreamhost.com/hc/en-us/articles/217555707-DNS-API-commands

Checklist

• Unit tests updated
• End user documentation updated

[linux-foundation-easycla]

• ❌ - login: @asymingt / name: Andrew Symington . The commit (8aca3c8) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

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[asymingt]

I tried to do the CLA but it's not enabled for individual contributors and so I was unable to sign it.