Retry on ETIMEDOUT timeout

[ehmicky]

Fixes #166.

When the TCP connection or HTTP request times out, an error with code: 'ETIMEDOUT' is usually thrown by node-fetch (as opposed to returning a 4** or 5**` error response).

This PR retries the request up to 10 times, with a fixed 5 seconds between each request. After that, it gives and propagate the ETIMEDOUT error.

[erezrokah]

Can't say I like this retry logic, but it is out of scope for this PR.

A backoff would be nice and a way to configure it and log it

[ehmicky]

Yes, absolutely, this could be much better.
I think it might interesting to use libraries for this too. For example, got has some rather intricate retry logic out-of-the-box.