Improve issue content for connection failures

[nijel]

When the connection to the server fails, the issue contains:

• HTTP code: 0
• Response time: 0 ms

That really doesn't give much information, see weblate-status-bot/nijel-status#3 for example.

The action log contains a bit more useful info: Got an error (on error) [Error: Couldn't connect to server]. Including that in the issue would be a good start.

What would be even better is providing the actual cause of the issue, for example:

• Did the DNS resolution fail?
• Was the connection to the server rejected?
• Was there an SSL handshake error?
• Was there connection timeout?

Using https://node-libcurl-docs.netlify.app/enums/_lib_enum_curlcode_.curlcode.html might be the way to figure out the actual reason.

I think it was a DNS issue in this particular case, but that's just my guess.