Update gpg.md

Author: nicholaswilde

docs/gpg.md

@@ -79,6 +79,7 @@ gpg --output revoke.asc --gen-revoke you@example.com
 
 ```shell
 gpg --export-secret-keys --armor my@email.com > /path/to/secret-key-backup.asc
+gpg --export --armor my@email.com > /path/to/public-key-backup.asc
 ```
 
 ## Keygrip to match `*.key` filenames in `~/.gnupg/private-keys-v1.d` directory