Add features list to readme

README.md

@@ -4,6 +4,16 @@
 
 ## Features
 
+* Written in ANSI C99, compatible with ``size_t`` and ``uintmax_t`` types for some specifiers
+* Implements output functions compatible with ``printf``, ``vprintf``, ``snprintf``, ``sprintf`` and ``vsnprintf``
+* Low-memory footprint, suitable for embedded systems
+* Reentrant access to all API functions
+* Requires single output function to be implemented by user for ``printf``-like API calls
+* With optional functions for operating systems to protect multiple threads printing to the same output stream
+* Allows multiple output stream functions (unlike standard ``printf`` which supports only one) to separate parts of application
+* Added additional specifiers vs original features
+* User friendly MIT license
+
 ## Contribute
 
 Fresh contributions are always welcome. Simple instructions to proceed::