Add WebSite structured data so that site title shows up in Google

[penelopeysm]

Closes #108 (I think, also I suppose Google will need to reindex the site, see https://developers.google.com/search/docs/crawling-indexing/ask-google-to-recrawl).

Note, I suspect we're running into this problem (emphasis mine, quoted from https://developers.google.com/search/docs/appearance/site-names):

Provide an alternative name. While our site name system tries to use your preferred site name, sometimes the name isn't available for use. For example, our system generally won't use the same site name for two different sites that are global in nature. In other cases, our system might determine that a site is more commonly recognized by an acronym than by a full name. Providing an alternative name using the alternateName property allows Google to consider other options if your preferred choice isn't selected.

Thus, the original <title> tag of Turing.jl isn't being picked up by Google, because the turing.ml domain already took that site title. I added an alternateName of The Turing Language to try to get around that.

[github-actions]

Preview the changes: https://turinglang.org/pr-previews/109
Please avoid using the search feature and navigation bar in PR previews!

[shravanngoswamii]

I don't think we have a better choice to do this until turing.ml expires!