Cache warning and errors from loader

[Strate]

There some loaders, (for example tslint-loader), which only emit warnings or errors. It would be useful to cache and re-emit that stuff with cache-loader.

[alexander-akait]

@Strate thanks for issue, PR welcome 👍

[jeron-diovis]

As I understand, for now, with cache-loader enabled and when there several files with linter errors, only warnings/errors from latest edited file are emitted. While normally results from all invalid files should be emitted.
Is it related to this issue?