Add short list of extensions that are provided by this collection to …

…README

Signed-off-by: Christoph Niethammer <[email protected]>

README.md

@@ -2,6 +2,13 @@
 
 Collection of extensions to the [Message Passing Interface (MPI) standard](https://www.mpi-forum.org/).
 
+The following extensions to the MPI standard are provided in this collection:
+
+| Function | Description |
+| -------- | ----------- |
+| MPI_Dims_weighted_create | Replacement of MPI_Dims_create that factorizes a number taking into account weights for the individual dimensions. This is usefull for creating an optimized Cartesian process topology. |
+| MPI_Info_set_json | Convinience funtion that sets (key, value) pairs to an MPI info object from a JSON string |
+
 ## Getting Started
 
 ### Prerequisites