Add example of passing data in Nunjucks macros

[kr8n3r]

Passing of stored data to Nunjucks macros is something we've seen being asked about.
This just adds the example code to the guidance, not replace the actual working example.

Addresses: #554 and #564

[joelanman]

Can we remove all the indent here? It adds unnecessary indent to the code example, because of the <pre>

[kr8n3r]

sure, updated

[hannalaakso]

Thanks for doing this @igloosi.

I suggest we make it clearer what page this code refers to (left a comment to this end).

When I place the macro in vehicle-features.html, it gets passed to "Check your answers" as an array of letters it looks like (see screen grab). I might be missing a step, would be good to document what's going wrong 🤔

[hannalaakso]

Suggest adding something like:

"The HTML example of this page is available on Vehicle features."

This would help to signpost to the relevant page and call out the Nunjucks/HTML distinction.

[joelanman]

we already tell people how to use checked in html on this page, so I don't think we need to do this too

[joelanman]

in a radio component macro
should be
in a checkbox macro (do we need 'component'?)

[kr8n3r]

this work doesn't update the example.
if we were to update it with macros then we'd need to remove the loop as well in the check-answers section

[joelanman]

Using a macro shouldn't break the behaviour here, something is odd

[kr8n3r]

yes, using radio macro in the features part instead of checkboxes. which i've updated now

[joelanman]

in a radio component macro
should be
in a checkbox macro (do we need 'component'?)

[joelanman]

Thanks!