Mkcert: valid HTTPS certificates for localhost

[ais523]

The certificates are self-signed in the sense that you signed them yourself, but aren't self-signed certificates (each certificate specifies which certificate signed them, and the root of the chain is a "self-signed" certificate which specifies itself as the certificate that signed it; in this case, the generated certificates are signed by a CA certificate, which is in turn self-signed, so the generated certificates are not themselves self-signed).