Rewrite `[ foo ] ++ bar` to `foo :: bar`?

[`elm-analyse`](https://github.com/stil4m/elm-analyse) gives a warning for this situation:

> If you concatenate two lists, but the [left hand side is a single element list literal], then you should use the cons operator.

This seems like not only a stylistic concern, but a performance optimization!

I can't think of any situations where it would be better to write e.g. `[ foo ] ++ anyOtherList` than `foo :: anyOtherList`. Should `elm-format` automatically perform this rewrite?

Start with the linked elm-analyse warning and elm-format's existing Elm rewrite behavior; the issue names no source file or test. Decide whether rewriting `[ foo ] ++ bar` to `foo :: bar` belongs in elm-format, then confirm the chosen behavior against the Elm Style Guide and formatter output.

Written by the indexing model from the issue text.