Add age encryption

I’m not sure why this hasn’t been included before. It’s one of the best encryption tools available today as a modern file encryption successor to gpg, built by one of the most reputable cryptographers in the world:

gopass (the password manager) also supports both gpg and age encryption modes.

More information: age and Authenticated Encryption

age also has a Rust alternative called rage.

Discussion continues from:

@dngray I’m not sure why we’d mention a tool in an advanced guide that isn’t recommended software, so we could probably add this to the CLI tools section we already have on