added waybar usage info

README.md

@@ -2,6 +2,21 @@
 sum proportional set size of every process for accurate memory usage statistics.
 In non-pretty mode, the number is given in kibibytes.
 
+This version is for use with [waybar](https://github.com/Alexays/Waybar). It
+outputs JSON that waybar can interpret using a 
+[custom module](https://github.com/Alexays/Waybar/wiki/Module:-Custom). 
+
+Here is an example configuration:
+```json
+"custom/pss-memory": {
+  "exec": "pss-total-waybar",
+  "return-type": "json",
+  "restart-interval": 3,
+  "format": "{} {icon}",
+  "format-icons": ["▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"]
+}
+```
+
 Licensed under GPLv3.
 
 ### Summary