update readme

plugins/common/shim/README.md

@@ -1,11 +1,11 @@
 # Telegraf Execd Go Shim
 
-The goal of this _shim_ is to make it trivial to extract an internal input plugin
+The goal of this _shim_ is to make it trivial to extract an internal plugin
 out to a stand-alone repo for the purpose of compiling it as a separate app and
-running it from the inputs.execd plugin.
-
-The execd-shim is still experimental and the interface may change in the future.
-Especially as the concept expands to processors, aggregators, and outputs.
+running it from one of the execd plugins:
+  - inputs.execd
+  - processors.execd
+  - outputs.execd
 
 ## Steps to externalize a plugin
 
@@ -40,6 +40,16 @@ Especially as the concept expands to processors, aggregators, and outputs.
   command = ["/path/to/rand", "-config", "/path/to/plugin.conf"]
   signal = "none"
 ```
+or
+```
+[[processors.execd]]
+  command = ["/path/to/rand", "-config", "/path/to/plugin.conf"]
+```
+or
+```
+[[outputs.execd]]
+  command = ["/path/to/rand", "-config", "/path/to/plugin.conf"]
+```
 
 ## Congratulations!