Make Sphinx generate a 404 page

[StanFromIreland]

Currently the docs 404 page is just the standard nginx page which has little features and does not have the Python Docs Header and footer. Most websites have a custom 404 page that is more helpful than the default.

My changes will result in Spinx building the page with the footer and header however the nginx conf must also be modified however this is up to the sysadmin as a PR cannot be submitted for it. I think this is what is required from a google search but I am not too familiar with nginx.

+ error_page 404 /404.html;
+ location = /404.html {
+     internal;
+ }

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📚 Documentation preview 📚: https://cpython-previews--128333.org.readthedocs.build/