[Release] Add missing post release tasks to dev/release/README.md

[kou]

Describe the enhancement requested

• Announce on dev@arrow.apache.org/user@arrow.apache.org/announce@apache.org
• Publish release blog post on https://arrow.apache.org/blog/
• Announce on LinkedIn https://www.linkedin.com/company/apache-arrow/ and BlueSky https://bsky.app/profile/arrow.apache.org
• Close the released milestone
• (Open a milestone for the next release?)

[assignUser]

Does it make sense to duplicate the list of tasks vs. linking to the release guide?

[kou]

You suggest that we improve https://arrow.apache.org/docs/developers/release.html for reusable (e.g. making "Announce the release on social media" linkable) and link to it from apache/arrow-java, right?

We can use the approach for them:

• Announce on dev@arrow.apache.org/user@arrow.apache.org/announce@apache.org
• Publish release blog post on https://arrow.apache.org/blog/
• Announce on LinkedIn https://www.linkedin.com/company/apache-arrow/ and BlueSky https://bsky.app/profile/arrow.apache.org

Others are apache/arrow-java specific.

[assignUser]

Oh wow sorry 🤦‍♂️ I didn't see that this was the Java repo. Ignore what I said°-°