Docs/use kedro sphinx theme

[Huongg]

Description

Fixes #1882

Development notes

QA notes

Checklist

• [ ] Read the contributing guidelines
• [ ] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [ ] Updated the documentation to reflect the code changes
• [ ] Added new entries to the RELEASE.md file
• [ ] Added tests to cover my changes

[astrojuanlu]

Hmmm don't know why, but instead of picking up kedro-sphinx-theme, the doc looks like sphinx-rtd-theme without our styling!

https://kedro--1898.org.readthedocs.build/projects/kedro-viz/en/1898/

[astrojuanlu]

Now that looks OK https://kedro--1898.org.readthedocs.build/projects/kedro-viz/en/1898/ ✔️