Support open graph

[Fil]

Design and implement a system (template? hook? options in frontmatter?) that allows the developer to add proper tags so that their page has the relevant information to create a "card" or "summary" on social platforms. Usually:

• the title
• an og:image (typically 1200 × 630)
• a description
• the canonical url (Generate link rel=canonical #179)

This needs the origin and base options (#180).

[mbostock]

Same comment as #179 (comment): this issue needs further specificity to be actionable.

[Fil]

This can be done with #253

[Fil]

Exposing meta data to the page could help in more scenarios. see #1036

[pettiross]

OG images would also let us show thumbnails for projects and pages on the platform.

[Fil]

related: #168

[pettiross]

+1 to using the front matter for this. We could expand on the front matter + observable.config.ts combination we have today so project-level defaults for OG metalabels could be set once and overridden on specific pages.

[mbostock]

Is this already done with the head option (and the ability to reference local assets in the head)?

[Fil]

Not quite yet. I'd like to explore a possibility for the head option (as well as header and footer) to be specified as a function, that would receive as arguments some meta data about the project config (including the origin option #180), and the current page (front matter, title, and possibly contents/files, if the user wants to insert an excerpt / summary or pick the first image from the contents) #1036. (Also mentioned #56 (comment).)

EDIT: I've now explored this and it's a pretty simple and straightforward change to getHtml() and it's not so simple.