infinite github.com in know_hosts

[xing0231]

ssh-agent/index.js

Line 30 in ea17a05

fs.appendFileSync(`${homeSsh}/known_hosts`, '\ngithub.com ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBEmKSENjQEezOmxkZMy7opKgwFB9nkt5YRrYMjNuG5N87uRgg6CLrbo5wAdT/y6v0mKV0U2w0WZ2YB/++Tpockg=\n');

from line 30 to 32 will keep adding the same key to know_hosts over and over by job running. could you add an option to add this to know_hosts or precheck know_hosts has the existing host alreaday? Or run a ssh-keyscan instead by child_process? Thank you!

[mpdude]

This is a duplicate of #106, happy to take patches!