Option for console.error warnings

[schinery]

After upgrading Formik in a project that doesn't use this reporter I noticed that I was getting warnings that were using console.error instead of console.warn, and so weren't outputted when showWarnings is set to true.

console.error
      Warning: An update to Formik inside a test was not wrapped in act(...).

Would it be possible to add entry.type === 'error' to the console filtering check for warnings?

[rickhanlonii]

Added, thanks for the PR!

[schinery]

Nice one! Already have the 0.5.0 version installed and working 👍🏻