OpenSSL, hashing & encryption commands

Copy-paste commands for the crypto tasks QA and devs hit constantly — a self-signed SSL certificate (PEM), private keys & CSRs, format conversion, file hashing, encryption/decryption, base64 and password-protected ZIPs — on 🪟 Windows, 🍎 macOS and 🐧 Linux. Hit Explain to see what each flag does.