feat: implement password authentication

[shtw]

Hello @jkuri thank you for creating this awesome tool!

I have added an authentication feature for both the server and client, based on feature request #42
The authentication method works similarly to set-id, where the client must provide a password to connect to the server.

Usage

Server

BORE_PASSWORD=mysecretpassword BORE_DOMAIN=example.com BORE_HTTPADDR=0.0.0.0:80 BORE_SSHADDR=0.0.0.0:2200 ./build/bore-server

Client

./build/bore -s example.com -p 2200 -ls localhost -lp 6500 -pw mysecretpassword

Please review the changes, and let me know if there's anything that needs improvement.
Looking forward to your feedback. Thanks!

[jkuri]

Hi @shtw, thank you for this PR! I did not tested it in action but everything looks legit. Can you please add this to the README documentation so other users will know how to use it?

[shtw]

Hi @shtw, thank you for this PR! I did not tested it in action but everything looks legit. Can you please add this to the README documentation so other users will know how to use it?

I've updated the README to include the authentication feature.