Update log collector plugin documentation

Change-Id: I110ef4fd199dbcb924c2c42363fe16b1204bbe3d
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/ffdc/docs/plugin.md b/ffdc/docs/plugin.md
index 337cb6d..36ac865 100644
--- a/ffdc/docs/plugin.md
+++ b/ffdc/docs/plugin.md
@@ -30,7 +30,7 @@
 
 ### Plugin Template Example
 
-plugins/foo_func.py
+Stand-alone functions: plugins/foo_func.py
 ```
 # Sample for documentation plugin
 
@@ -41,6 +41,17 @@
     return 1
 ```
 
+Class function(s): plugins/plugin_class.py
+```
+class  plugin_class:
+
+    @staticmethod
+    def plugin_print_msg(msg):
+        print(msg)
+```
+
+This is to avoid passing object self in plugin args YAML when calling the class function(s).
+
 You can add your own plugin modules to extend further.
 
 Test your plugin: