peltool: Add Notes from message registry file

Add the Notes section found in the message registry file to the json
output (if it's present and not empty).

Example:

"Error Details": {
    "Message":  "Unknown (Original event not in message registry)",
    "Notes": [
                "This is used when the actual error name isn't",
                "found in the registry."
    ]
}

Signed-off-by: Harisuddin Mohamed Isa <harisuddin@gmail.com>
Change-Id: I69773547c06f6361055c2f0decd07967d0012946
diff --git a/extensions/openpower-pels/registry.hpp b/extensions/openpower-pels/registry.hpp
index c3b3bc0..0314081 100644
--- a/extensions/openpower-pels/registry.hpp
+++ b/extensions/openpower-pels/registry.hpp
@@ -59,6 +59,11 @@
      *        in the Message field.
      */
     std::optional<std::vector<std::string>> messageArgSources;
+
+    /**
+     * @brief An optional vector of string that forms the Notes field.
+     */
+    std::optional<std::vector<std::string>> notes;
 };
 
 /**