add og graph meta data to header
See #466 (closed)
The site has no open graph meta data, or any meta data actually.
This adds the minimum of og:graph and other meta data.
- Conditional on what is available.
- Because we don't set a description or excerpt, it truncates the first 130 characters.
- The image is pulled from the image_title set in blog posts, but ultimately we don't set a feature image of any sort of other pages, e.g., the team page.
But... we'd need to have an image setting on the default page layout, I think?