chore(build): Add a CI workflow to build and push multiubuntu image whenever a change detected

[sikehish]

Purpose of PR?: Add a CI workflow to build and push the multi-architecture Ubuntu-based image for KubeArmor on changes to the main branch.

Fixes #1876

Does this PR introduce a breaking change? No

If the changes in this PR are manually verified, list down the scenarios covered::

• Verified that the CI workflow builds the Docker image successfully using multi-architecture (amd64 and arm64) support.
• Confirmed that the Docker image pushes correctly to Docker Hub when the workflow is triggered by push or pull_request on the main branch.

Additional information for reviewer? : This PR introduces a new CI workflow and is not dependent on any previous PR or design.

Checklist:

• [ ] Bug fix. Fixes N/A
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [x] PR Title follows the convention of <type>(<scope>): <subject>
• [ ] Commit has unit tests
• [ ] Commit has integration tests