fix(error handler): add default handler to econnreset

[chimurai]

Description

Add default handler to http-proxy econnreset event.

This event is not documented in official documentation:
https://github.com/http-party/node-http-proxy#listening-for-proxy-events

It is typed in:
https://github.com/DefinitelyTyped/DefinitelyTyped/blob/e626d3221693ea35ae4298bc8192ac4abebd225f/types/http-proxy/index.d.ts#L109

Event is emitted:
https://github.com/http-party/node-http-proxy/blob/9b96cd725127a024dabebec6c7ea8c807272223d/lib/http-proxy/passes/web-incoming.js#L158

Motivation and Context

Lack of this handler potentially causes server to crash (unconfirmed, difficult to replicate)

• Hard to catch error on proxying in Node.js 10 webpack/webpack-dev-server#1642
• fixes hpm 1.0.6 Erroring for sockets when target server is restarted  #476
• fixes ECONNRESET error from the proxy inside EKS kubernetes clusters #648

How has this been tested?

hotfix 🤞

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[coveralls]

Coverage decreased (-0.3%) to 98.584% when pulling 20988a2 on econnreset into 4baae76 on 2.x.