Improving transcode dataset docs

[ElenaKhaustova]

Description

Solves #3676

Development notes

• Renamed the section in the docs, so it contains transcoding dataset reference;
• Provided some details on how the transcoding mechanism works;
• Kept an example with pyspark as recommended one;
• Added a new section with incorrect examples of using transcoding and the corresponding explanations.

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Checklist

• [ ] Read the contributing guidelines
• [ ] Signed off each commit with a Developer Certificate of Origin (DCO)
• [ ] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [ ] Updated the documentation to reflect the code changes
• [ ] Added a description of this change in the RELEASE.md file
• [ ] Added tests to cover my changes
• [ ] Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[AhdraMeraliQB]

See built docs

[ElenaKhaustova]

Leave some comments but I think we should really add validation instead of trying too hard to explain this if possible.

Applied suggested changes, thank you!

As for validation, it's already there. The section How *not* to use transcoding aims to clarify the logic behind transcoding and point to potential issues. Though it's good to know if the explanations are unclear.