DAS-2070 - Update README to describe new CI/CD.

[owenlittlejohns]

Description

This PR updates the README to ensure the description of the repository is now up-to-date and refers to GitHub workflows instead of Bamboo build plans or deployment projects.

Jira Issue ID

DAS-2070

Local Test Steps

N/A (just check the README looks accurate)

PR Acceptance Checklist

• [x] Jira ticket acceptance criteria met.
• CHANGELOG.md updated to include high level summary of PR changes.
• docker/service_version.txt updated if publishing a release.
• Tests added/updated and passing.
• [x] Documentation updated (if needed).