Add structured data for question pages

[MoshiKoi]

Working on #906

This should work, as shown here, but I'm not sure why the preview doesn't. If you have any insights, please let me know; I'm not familiar with SEO things.

[ullallulloo]

Google is very unpredictable about what previews it shows. I don't know why the preview doesn't show up in Google's tool, but I don't see how it could be anything wrong with the schema data.

[cellio]

This has been in draft state for a while. What additional work do we need to do?

[MoshiKoi]

Honestly forgot I made this whoops

The main thing is that I have no way of actually knowing whether it works or not until it gets put on the server and I see if Google does the preview when I search. As mentioned above, Google's test page doesn't preview it correctly, so I'm not sure the generated schema is correct.

Maybe it could be put on the dev server to test...? I'm not sure if it's indexed.

[cellio]

If it doesn't work, will the change do any harm? (I gather not?) @ArtOfCode- , do you have an opinion on this?

[ullallulloo]

Note that I made a PR on @MoshiKoi 's fork fixing a couple of bugs, but besides that I would say it should be merged. Providing the data can only help.