docs(blog): add post on stream-batch unification (#8293)

<!--
Thanks for taking the time to contribute to Ibis!

Please ensure that your pull request title matches the conventional
commits
specification: https://www.conventionalcommits.org/en/v1.0.0/
-->

## Description of changes

<!--
Write a description of the changes commensurate with the pull request's
scope.

Extremely small changes such as fixing typos do not need a description.
-->

Add a new blog post on stream-batch unification.