Add index to docs samples

[RogerHowellDfE]

I suggest that a useful addition to the tag helper library would be a reference site, where it is possible to see both the rendered HTML component alongside the code (tag helpers) used to generate it.

• Upstream publishes a review app with components shown/listed on one page, with an index linking to each one in isolation. For example: https://govuk-frontend-pr-5574.herokuapp.com/components . This shows only the rendered component and HTML, not tag-helpers.

• Similarly, the design system site itself shows component examples: https://design-system.service.gov.uk/components/ . This includes the rendered component and HTML/nunjucks code, not tag-helpers.

• The GitHub repo has some *.md files which are able to be viewed on GitHub: https://github.com/gunndabad/govuk-frontend-aspnetcore/tree/main/docs/components . These include screenshots of the rendered component (i.e., not HTML) and hard-coded examples of the tag-helpers (note: not guaranteed to be consistent with the samples project and the screenshot).

This draft PR is a stepping stone towards a reference site, introducing a similar index page.

Before I run too far with it, is this kind of docs site something that would be welcomed?

Notes:

• I have not added any new samples and I have not modified pre-existing examples
  • The code in this PR should dynamically pick up any additional samples that do get added
• It does not publish it as a review app for now (it must be run locally as currently is the case).
  • I do wonder if we could use wget or similar to pull a copy of the generated HTML pages and host that static HTML on GitHub Pages?
• I see that there is additional information in the docs/ directory
  • If we were to run with publishing a GitHub pages site, these could be incorporated too?

Screenshot:

[gunndabad]

Before I run too far with it, is this kind of docs site something that would be welcomed?

Yes, definitely. I'd like to move towards a 'proper' doc site ultimately. I'll have a think about how to split up the tasks around this. https://govuk-components.netlify.app/ is some nice prior art

[sussexrick]

FYI we have partially what you're looking for, though not as comprehensive as you're suggesting. It's not published online so you have to clone our repo and run it.

https://github.com/thepensionsregulator/govuk-frontend-aspnetcore-extensions/blob/develop/docs/aspnet/run-example-application.md