Add plugin uses to the readme

Author: Bruno Sutic

README.md

@@ -4,6 +4,12 @@ Tmux plugin that enables displaying online status for your workstation.
 
 Introduces a new `#{online_status}` format.
 
+This plugin is useful if:
+- you spend most of your time in Tmux and don't want to "switch" to gui to
+  check whether you're connected.
+- you have a flaky internet connection and you don't want to be surprised
+  when a simple `curl` or `wget` fails because the connection just broke.
+
 ### Usage
 
 Add `#{online_status}` format string to your existing `status-right` tmux