Added Cunningham's Law (#149)

README.md

@@ -17,6 +17,7 @@ Laws, Theories, Principles and Patterns that developers will find useful.
     * [Amdahl's Law](#amdahls-law)
     * [Brooks' Law](#brooks-law)
     * [Conway's Law](#conways-law)
+    * [Cunningham's Law](#cunninghams-law)
     * [Dunbar's Number](#dunbars-number)
     * [Gall's Law](#galls-law)
     * [Hanlon's Razor](#hanlons-razor)
@@ -113,6 +114,16 @@ See also:
 
 - [The Spotify Model](#the-spotify-model)
 
+### Cunningham's Law
+
+[Cunningham's Law on Wikipedia](https://en.wikipedia.org/wiki/Ward_Cunningham#Cunningham's_Law)
+
+According to Steven McGeady, Ward Cunningham advised him in the early 1980s: "The best way to get the right answer on the Internet is not to ask a question, it's to post the wrong answer." McGeady dubbed this Cunningham's law, though Cunningham denies ownership calling it a "misquote." Although originally referring to interactions on Usenet, the law has been used to describe how other online communities work (e.g., Wikipedia, Reddit, Twitter, Facebook).
+
+See also:
+
+- [XKCD 386: "Duty Calls"](https://xkcd.com/386/)
+
 ### Dunbar's Number
 
 [Dunbar's Number on Wikipedia](https://en.wikipedia.org/wiki/Dunbar%27s_number)