docs(context-mgmt): add documentation for context management library

This patch adds some documentation for the context management library.
It mainly covers the design at a higher level, with more focus on
the cold boot and warm boot entries as well as the operations
involved during context switch. Further it also includes a section
on feature enablement for individual world contexts.

Change-Id: I77005730f4df7f183f56a2c6dd04f6362e813c07
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
diff --git a/docs/design_documents/context_mgmt_rework.rst b/docs/design_documents/context_mgmt_rework.rst
index 59f9d4e..b086e3c 100644
--- a/docs/design_documents/context_mgmt_rework.rst
+++ b/docs/design_documents/context_mgmt_rework.rst
@@ -4,7 +4,7 @@
 :Authors: Soby Mathew & Zelalem Aweke
 :Organization: Arm Limited
 :Contact: Soby Mathew <soby.mathew@arm.com> & Zelalem Aweke <zelalem.aweke@arm.com>
-:Status: RFC
+:Status: Implementation is ongoing. Refer to :ref:`Context Management Library` for more details.
 
 .. contents:: Table of Contents
 
@@ -194,4 +194,4 @@
 
 --------------
 
-*Copyright (c) 2022, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2022-2024, Arm Limited and Contributors. All rights reserved.*