expose the internal 'econreset' error event in proxy options

[NiccsJ]

Describe the feature you'd love to see

In reference to #763 & #759

As of now, only a default log is being printed in these events, there's no way for the user to implement custom logic if these events occur.
Would be great if either this event can be mapped to the 'onError' event handler, or if separate user-defined event handlers can be accepted just like the rest of the events.

current implementation

    proxy.on('econnreset', (error, req, res, target) => {
        logger.error(`[HPM] ECONNRESET: %O`, error);
        console.log('HERE');
    });
    // https://github.com/webpack/webpack-dev-server/issues/1642#issuecomment-1104325120
    proxy.on('proxyReqWs', (proxyReq, req, socket, options, head) => {
        socket.on('error', (error) => {
            logger.error(`[HPM] WebSocket error: %O`, error);
        });
    });
    logger.debug('[HPM] Subscribed to http-proxy events:', Object.keys(handlers));
}

My workaround code

    proxy.on('econnreset', handlers['error']);
    // https://github.com/webpack/webpack-dev-server/issues/1642#issuecomment-1104325120
    proxy.on('proxyReqWs', (proxyReq, req, socket, options, head) => {
        socket.on('error', (error) => {
            logger.error(`[HPM] WebSocket error: %O`, error);
        });
    });
    logger.debug('[HPM] Subscribed to http-proxy events:', Object.keys(handlers));
}

Additional context (optional)

No response