rimage: add ipc4 extended module config introduction

This is a introduction of ipc4 extended module config and
how to add this information in the xxx.toml for template.

Signed-off-by: Rander Wang <[email protected]>

Author: RanderWang

developer_guides/rimage/index.rst

@@ -19,7 +19,7 @@ For more details see:
    :maxdepth: 1
 
    extended_manifest
-
+   ipc4_extended_module_config
 
 
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