Update readme.txt (#87)

***NO_CI***

Author: josesimoes

source/readme.txt

@@ -10,7 +10,7 @@ API docs: https://docs.nanoframework.net/api
 
 Browse our samples repository: https://github.com/nanoframework/samples
 
-Check our documentation online: https://docs.nanoframework.net/articles/intro.html
+Check our documentation online: https://docs.nanoframework.net
 
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