feat: Add docs for makeplane for self-hosted Sentry.

[Asynchronite]

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[vercel]

@Asynchronite is attempting to deploy a commit to the Sentry Team on Vercel.

A member of the Team first needs to authorize it.

[aldy505]

I personally dislike having subheadings for Sentry SaaS and Sentry Self-Hosted. Why don't we just put a simple bold text, since it's just less than 3 steps?

[Asynchronite]

What do you mean? How would you want me to structure this?