refactor RCCL (#1112)

* refactor RCCL

* rccl updates

* Update index.rst

* refactor

* Update what-is-rccl.rst

docs/api-library.rst

@@ -0,0 +1,11 @@
+.. meta::
+   :description: RCCL is a stand-alone library that provides multi-GPU and multi-node collective communication primitives optimized for AMD GPUs
+   :keywords: RCCL, ROCm, library, API
+
+.. _api-library:
+
+=============
+API library
+=============
+
+.. doxygenindex::