this takes what i love about 'next/meta' (originally imported via my
'next-metadata' port) and consolidates it into a simple 250 line
library. instead of supporting all meta tags under the sun, only the
most essential ones are exposed. less common meta tags can be added with
JSX under the 'extra' field.
a common problem i had with next-metadata was that open graph embeds
copied a lot of data from the main meta tags. to solve this, a highly
opiniated 'embed' option exists, which simply passing '{}' will trigger
the default behavior of copying the meta title, description, and
canonical url into the open graph meta tags.
"server side rendering" is a misleading term since it implies there is a
server. that isn't neccecarily the case here, since it supports running
in the browser. I think "clover engine" is cute, short for "clover html
rendering engine". Instead of "server side rendering", it's just rendering.
This commit makes things a lot more concise, such as `ssr.ssrAsync`
being renamed to `render.async` to play nicely with namespaced imports.
`getCurrentRender` and `setCurrentRender` are just `current` and
`setCurrent`, and the addon interface has been redesigned to force
symbols with a wrapping helper.
