add hello message

when you start up a connector, it would be good if it notifies its neighbors ('hello, I'm awake, send me all your routes please'), so that you don't have to wait 30 seconds before an ilp-kit starts working.

The connector broadcasts its local routes on startup, why does it need a separate "hello" message?

so that it also receives asap

If a connector receives a new route, it broadcasts immediately (https://github.com/interledgerjs/ilp-connector/blob/d2e600bd990c72425728753c27d3e094b9a30009/src/lib/message-router.js#L145-L152).

ok, so then this would not be necessary, provided the downtime was long enough to make previously broadcasted routes expire, and provided that your peer correctly noticed you have been down and that you missed out on their last few broadcasts.