Remote Write 2.0: Write a blog post (when stable)

### Proposal

Part of https://github.com/prometheus/prometheus/issues/13105

As proposed on community meeting by @gouthamve the plan is to write blog post, potentially now when we announce 2.0-RC.0 spec (experimental status).
