Add a notebook on code decompilation using a function decorator.

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Added a new notebook titled "Code Decompilation with a Decorator" in the advanced Python folder to demonstrate how to inspect and decompile function code using a Python decorator. This involved creating a function decorator that prints out the details and decompiled source code of a given function before executing it. The relevant changes were made to include this notebook in the "_toc.yml" under the Advanced techniques section.

closes #69