Report Chokidar errors

[novemberborn]

Watch mode uses chokidar to detect changes. Chokidar can emit error events. Currently these are ignored. We should report them to the user instead as they may include clues as to why the watcher isn't detecting changes.

For example #1030 was due to Chokidar watching more files than the system allowed.

I'm thinking this should be part of the watcher's debug output, but that still takes some effort to find. Should it go in the verbose output instead?

We'll have to reproduce #1030 with this reporting enabled to see if Chokidar actually reports the errors and if it's informative enough.

[fabiospampinato]

Kind of tangential and I'm biased on this, but it might be worth exploring replacing chokidar with watcher, which could be more refined for what this library needs (native watching under windows, much better handling of EMFILE errors, rename detection...).

[novemberborn]

This would be irrelevant if #3123 is completed.