Warning on sass-loader 13

[garak]

With the latest version of webpack-encore (2.1.0) I get this warning:

WARNING Webpack Encore requires version ^12.0.0 of sass-loader. Your version 13.0.0 is too new. The related feature may still work properly. If you have issues, try downgrading the library, or upgrading Encore.

[weaverryan]

Looks like we need to bump our dependency range in package.json to allow 13. Then the tests can validate it’s working. But the warning is just that: it likely works fine, but encore hasn’t been tested with it yet :). I’d be happy if someone made a PR.