feat(design-land): add file tabs back to code preview and allow content to be hidden

[xelaint]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/graycoreio/daffodil/blob/develop/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

File tabs are not included in the code preview. The content for examples are always shown.

Fixes: #2568

What is the new behavior?

Add file tabs because some design examples benefit from seeing the component implementation. Add property to hide or show example content. This is beneficial if I want to display a block of formatted code without wanting to display the content.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information