Support for generic linters that run on all (most?) filetypes

ALE should be able to support a linter that checks all (or some number of) filetypes. I want to add support for [Codespell](https://github.com/codespell-project/codespell), but as-is I think I would need to follow the pattern of how Redpen is implemented (multiple almost identical files). In the case of Redpen, it actually needs slightly different configuration for certain file types, and it's only checking a subset of typesetting or documentation filetypes.

Codespell doesn't need different options for different types of files, and it presumably would work well for a much larger number (all?) filetypes, so I think an alternative approach is worth discussing.

If this a bad idea, I'd like a suggestion on a less-bad idea for adding Codespell support to a wide range of filetypes without lots of code duplication.