Feature: Enable separate metadata for different SPA page views for social sharing

[terichadbourne]

Although analytics via Countly (PR #257) will successful capture page views separately for different views/routes in our SPA, we still have the challenge of only being able to have a single set of metadata for things like social card generation. Opening a new issue here as a spinoff of #179 which will be closed shortly.

Shared by @mikeal: we could use this to get the right card info (open graph metadata) on different pages https://github.com/chrisvfritz/prerender-spa-plugin