docs(blog): add post introducing the Flink backend (#7912)

<!--
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.
-->

Port https://github.com/claypotai/ibis-flink-example to a
quickstart/blog post.

## Issues closed

<!--
Please add Resolves #<issue number> (no angle brackets) if this pull
request
resolves any outstanding issues.

For example, if your pull requests resolves issues 1000, 2000 and 3000
write:

* Resolves #1000
* Resolves #2000
* Resolves #3000

If your pull request doesn't resolve any issues, you can delete this
section
entirely, including the `## Issues closed` section header.
-->
Resolves #7739