Add self-hosted option to action (#52)

+ This skips over the SSH configuration part of the action.
+ This is because self-hosted runners would typically have SSH already running causing ssh-agent command to throw an error (process already exists/port in use)

action.yaml

@@ -8,6 +8,11 @@ inputs:
     required: true
     description: The command.
 
+  self-hosted:
+    required: false
+    default: 'false'
+    description: Whether the action is running on a self-hosted runner.
+
   private-key:
     required: false
     default: ''