Docs: Add a docs page for PythonCodeSplitter

[julian-risch]

We added a new PythonCodeSplitter component in #11380 and now we need to add a documentation page to https://github.com/deepset-ai/haystack/tree/main/docs-website/docs/pipeline-components/preprocessors and list the new component in https://github.com/deepset-ai/haystack/blob/main/docs-website/docs/pipeline-components/preprocessors.mdx

[AbdullahUsama]

I'd love to take this up and write the documentation, can I start working on it if no one is assigned on this yet?