docs: update showcase-docs to be compatible with Docusaurus

[schultzp2020]

Description

Please explain the changes you made here.

Which issue(s) does this PR fix

• References Improve the website documentation page janus-idp.github.io#263

PR acceptance criteria

Please make sure that the following steps are complete:

• GitHub Actions are completed and successful
• Unit Tests are updated and passing
• E2E Tests are updated and passing
• Documentation is updated if necessary (requirement for new features)
• Add a screenshot if the change is UX/UI related

How to test changes / Special notes to the reviewer

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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[nickboldt]

seems legit but would want 👀 from the Doc team too, since we use asciidoctor and pantheon, not docusaurus

[schultzp2020]

@hmanwani-rh can you please take a look? This is blocking the mentioned issue.

[openshift-merge-robot]

PR needs rebase.

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