docs: add DeployHQ to deployment doc

[MartaKar]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

This PR adds DeployHQ as a deployment option to the Docusaurus deployment documentation.

Test Plan

Tested locally

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

[netlify]

✅ [V2]

Built without sensitive environment variables

Name	Link
🔨 Latest commit	fa6e84b
🔍 Latest deploy log	https://app.netlify.com/projects/docusaurus-2/deploys/6911cfbbb938400008d689ec
😎 Deploy Preview	https://deploy-preview-11539--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

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[slorber]

Hi

I'm sorry, but we are not accepting more deployment platforms on this page