Minor style fixes

Author: josesimoes

README.md

@@ -158,6 +158,6 @@ The **nanoFramework** Class Libraries are licensed under the [MIT license](LICEN
 This project has adopted the code of conduct defined by the Contributor Covenant to clarify expected behaviour in our community.
 For more information see the [.NET Foundation Code of Conduct](https://dotnetfoundation.org/code-of-conduct).
 
-### .NET Foundation
+## .NET Foundation
 
 This project is supported by the [.NET Foundation](https://dotnetfoundation.org).