feat: improve the Readme.md for banner and banner content

[testcara]

For https://issues.redhat.com/browse/KFLUXUI-587

This PR improves the README.md for the Konflux Info banner guide and updates the banner-content.yaml files for specific clusters to include a banner inviting users to try the new feature and reference the documentation.

The background is:
The UI PR(konflux-ci/konflux-ui#319) for banner is almost ready and would be merged before the end of this week. I would deploy the UI change to staging this week or early days of next week.

With this current PR :

1. Users would get the clear guide about how to add banners(one-time or repeated banner).
2. Once the PR is merged, users would see the below banner in staging konflux to be aware of the feature.

[openshift-ci]

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[testcara]

/retest