Update README.md

Author: witold-swierzy

data-platform/autonomous-database/autonomous-json/document_format_conversion_api/README.md

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-test to be added later
+This repo contains PL/SQL API for document conversion demonstrating how it is possible to abstract from a particular format (XML or JSON) and work on the data.
+**doc** directory contains documentation, including overview presentation and user guide
+**sql** directory contains API code with scripts allowing easy installation and removal
+**demo** directory contains script demonstrating functionality of the API
+
+# License
+
+Copyright (c) 2025 Oracle and/or its affiliates.
+
+Licensed under the Universal Permissive License (UPL), Version 1.0.
+
+See [LICENSE](https://github.com/oracle-devrel/technology-engineering/blob/main/LICENSE) for more details.
+
+