Social media meta tags for Facia and Tag pages

The new meta tags help compose more relevant snippets when shared on social media:
`twitter:card`
`twitter:url`
`og:description`
`og:title`
`og:image`
Please make another pull request and fix this (now that you've merged this one ...). An `if` will definitely compile here.

```scala
if (tag.bio.nonEmpty) {
  Some(tag.bio)
} else {
  tag.description
}
```

You're not using the case expression for anything here.