Add safeguard for missing jq in the system (#24)

Warn developer for missing package, as original error message does not say this straight.

Another more "polluted" options is 
```
command -v jq &> /dev/null && echo Latest synced block behind by: \
$((($( date +%s )-\
$( curl -s -d '{"id":0,"jsonrpc":"2.0","method":"optimism_syncStatus"}' -H "Content-Type: application/json" http://localhost:7545 |
   jq -r .result.unsafe_l2.timestamp))/60)) minutes || { echo "mvn is not installed" 1>&2 ; }
```