RedfishPkg/library: EDK2 port of jansson library

edk2 JsonLib which is the edk2 port of open source
jansson library.
(https://github.com/akheron/jansson)
jansson library is the open source project to manipulate
JSON data structure.

Signed-off-by: Abner Chang <abner.chang@hpe.com>

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Nickle Wang <nickle.wang@hpe.com>
Cc: Peter O'Hanley <peter.ohanley@hpe.com>
Reviewed-by: Nickle Wang <nickle.wang@hpe.com>
Acked-by: Leif Lindholm <leif@nuviainc.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>

RedfishPkg/Library/JsonLib/Readme.rst

@@ -0,0 +1,35 @@
+=============================================================================
+                             Introduction
+=============================================================================
+  Jansson is a C library for encoding, decoding and manipulating JSON data.
+Its main features and design principles are:
+
+  - Simple and intuitive API and data model
+  - Comprehensive documentation
+  - No dependencies on other libraries
+  - Full Unicode support (UTF-8)
+  - Extensive test suite
+
+  Jansson is licensed under the MIT license(refer to ReadMe.rst under edk2).
+It is used in production and its API is stable. It works on numerous
+platforms, including numerous Unix like systems and Windows. It's suitable
+for use on any system, including desktop, server, and small embedded systems.
+
+  In UEFI/EDKII environment, Redfish project consumes jansson to achieve JSON
+operations.
+
+* Jansson version on edk2: 2.13.1, API reference is on the below URL,
+  https://jansson.readthedocs.io/en/2.13/apiref.html
+
+* EDKII jansson library wrapper:
+   - JsonLib.h:
+     This is the denifitions of EDKII JSON APIs which are mapped to
+     jannson funcitons accordingly.
+
+*Known issue:
+   Build fail with jansson/src/load.c, add code in load.c to conditionally
+   use stdin according to HAVE_UNISTD_H macro. The PR is submitted to
+   jansson open source community.
+   https://github.com/akheron/jansson/pull/558
+
+