Action hangs awaiting user input if ssh key password-protected

[Kristina-Pianykh]

It would be nice to have some feedback when a user accidentally picks a password-protected ssh key. This results into the action hanging indefinitely prompting a user for the password.

Example:

| Starting ssh-agent
| SSH_AUTH_SOCK=/tmp/ssh-XXXXXXi8BQfy/agent.108
| SSH_AGENT_PID=109
| Adding private key(s) to agent

The line in question:

ssh-agent/dist/index.js

Lines 358 to 360 in a6f90b1

	privateKey.split(/(?=-----BEGIN)/).forEach(function(key) {
	child_process.execFileSync(sshAddCmd, ['-'], { input: key.trim() + "\n" });
	});

Would be great to have some mechanism in place to abort with a warning/error message that no password-protected ssh key is allowed