Style: add .astyleignore file

0xc0170 · 0xc0170 · commit c14a19c1cef0 · 2018-02-07T11:05:04.000Z
diff --git a/docs/reference/contributing/guidelines/style.md b/docs/reference/contributing/guidelines/style.md
@@ -14,6 +14,8 @@ Whether you're writing new code or fixing bugs in existing code, please follow t
 
 Mbed OS follows the [K&R style](https://en.wikipedia.org/wiki/Indent_style#K.26R_style), with at least two exceptions (which can be found in the list below the code sample).
 
+The only exception to this coding style are 3rd parties libraries. The 3rd party libraries should be added to the `..astyleignore` file located in the Mbed OS root directory.
+
 ##### Code sample
 
 ```c
