Use filetypes over mime-types for syntax highlighting

Non traditional types like `tsx` default to the `application/octect-stream` mime-type. During a fetch (initial load) `tsx` will have a mime-type of `application/octect-stream` and will not have syntax highlights as a consequence.

Currently, we use `mime-types` to infer syntax highlighting. However, servers are less than consistent with `mime-types`.

It is possible to avoid `mime-types` entirely and instead highlight by `file-type`.