ci(PPDSC-2471): update DOCKER_TAG to enable deploys from main

[evgenitsn]

PPDSC-2471

What

Updated DOCKER_TAG in config.yml file to differentiate a dev vs prod vs release builds.

We need this in order to fix the approve_publish_docs_&_storybook step and manually release docs and storybook from main. This is step one of the ticket.
After this gets merged I will test the above step and if it works then I will open another PR for removing that manual step and enable docs deploy on every merge to main.

I have done:

• Written unit tests against changes
• Written functional tests against the component and/or NewsKit site
• Updated relevant documentation

I have tested manually:

• The feature's functionality is working as expected on Chrome, Firefox, Safari and Edge
• The screen reader reads and flows through the elements as expected.
• There are no new errors in the browser console coming from this PR.
• When visual test is not added, it renders correctly on different browsers and mobile viewports (Safari, Firefox, small mobile viewport, tablet)
• The Playground feature is working as expected

Before:

After:

Who should review this PR:

How to test:

[newskit-engineering]

You can preview these changes on:
Documentation Site: http://ncu-newskit-docs.s3-website-eu-west-1.amazonaws.com/ppdsc-2471-update-circle-ci-docker-tag-to-deploy-from-main
Storybook: http://ncu-newskit-docs.s3-website-eu-west-1.amazonaws.com/ppdsc-2471-update-circle-ci-docker-tag-to-deploy-from-main/storybook