feat: Add slug for multiple domains of same user

README.md

@@ -18,11 +18,16 @@ static_sites:
   - user: host_1
     domain: host_1.example.org
     key: "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMOREPUBLICKEYINFO host_1"
+    slug: host-1-staging
   - user: host_2
     domain: host_2.example.org
     key: "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMOREPUBLICKEYINFO host_2"
+    slug: host-1-prod
 ```
 
+You can re-use a user and their key. You can also use different keys per user. Be aware that a shared user or keys will allow any such site to alter all sites that share the user/key.
+
+
 Now deploy by running
 
 ```zsh