Create bluesky release announcement action

[CalvinWilkinson]

Complete The Item Below

• I have updated the title without removing the 🚧 emoji.

Description

Create a custom action to send release announcements on Bluesky. This will be very similar to the X release announcement action.
It will replace template variables, load a template from a repository or locally, and then send the post.

For sending the blue sky post, use the already existing GitHub action named Send Bluesky Post on the marketplace.

Acceptance Criteria

The items to complete to satisfy the Definition of Done.

• All the unit tests have been executed and passed locally after PR work is complete. (Why? Refer to 'Additional Information' below.)
• A new action has been created to send release announcements on bluesky.

ToDo Items

The items to complete to satisfy the Definition of Done.

• Add a priority label to the issue. Refer to the Priority Type Labels section below.
• Link the issue to the correct milestone (if applicable).

Code of Conduct

• I agree to follow this project's Code of Conduct.