Update ssh.markdown

source/_addons/ssh.markdown

@@ -9,4 +9,16 @@ sharing: true
 footer: true
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-[Placeholder]
+Setup a [ssh](https://openssh.org/) server. Allow to access severals hass.io folders with ssh client. It allow also to do some tunneling for access from outside. It should by used only on a ResinOS platform, generic linux would have here own ssh server.
+
+```json
+{
+  "authorized_keys": [
+    "ssh-rsa AKDJD3839...== my-key"
+  ]
+}
+```
+
+Option variables:
+
+- **authorized_keys** (*Required*): default empty. Your public-keys for authorized keyfile. Every element will be a line inside that file.