Unknown languages crash render

[isaacwhite]

Context (Environment)

Observed this in the logs on our own copy of Library, which should not be causing a 500.

'Unknown language: "archieml"'

This is probably coming from the new syntax highlighting code added in the most recent release.

Expected Behavior

When the language is unknown, we should render without syntax highlighting.

Actual Behavior

The app returns a 500 until the unknown language is removed

To Reproduce

Try creating a code snippet where the language is archieml

Possible Solution

Use a try/catch in this section of the formatter code, so that errors thrown by hljs are nonfatal: https://github.com/nytimes/library/blob/master/server/formatter.js#L112-L116