Provide opengraph metadata for history pages

[robsiemb]

To help things like discord and facebook render our pages better when they are linked (especially, say, buggy and org pages), we should embed some of the opengraph data in them (especially og:image).

e.g. today if you post https://cmubuggy.org/history/buggy/conquest to discord, you get a flat link that says "History | CMU Buggy Alumni Association" and no image. We can do... much better if we just embed a bit of metadata....

See: https://ogp.me/

[robsiemb]

Ideally we could find a way to do this at least for /history/buggy and /history/org. It is a bit awkward though since we're well past the section of the document when we actually start doing the history queries...

[robsiemb]

Still need to flesh this out a bit more, but a basic framework is in place now.