Add script for Plausible analytics

[reshamas]

Example in scikit-learn.org:

https://github.com/scikit-learn/scikit-learn/blob/main/doc/conf.py

    "analytics": {
        "plausible_analytics_domain": "scikit-learn.org",
        "plausible_analytics_url": "https://views.scientific-python.org/js/script.js",
    },

blog.scikit-learn.org

Should the update happen in this file?
https://github.com/scikit-learn/blog/blob/main/_config.yml

Example conf.py file

https://github.com/scikit-learn/scikit-learn/blob/main/doc/conf.py

[reshamas]

The blog URL has been registered. JavaScript code can be added:

<script defer data-domain="blog.scikit-learn.org" src="https://views.scientific-python.org/js/script.js"></script>