Use logo_url instead of "logo", removed in Sphinx 6

[Qeole]

In commit sphinx-doc/sphinx@ac0fc4b78173 (Remove more deprecated items in Sphinx 6.0 (#10562)), Sphinx removed the deprecated variables logo and favicon, in favour of logo_url and favicon_url, respectively. As a consequence, including the logo defined in html_logo no longer works when the sphinx_material theme is used with Sphinx >= 6.

Let's use logo_url if available in header.html. We also use it in sidebar.html, although this one doesn't matter much because CSS class md-nav__button gets a display:none in application.css.

[Qeole]

As a side note (and not related to this PR), I'd be curious to understand how file sphinx_material/sphinx_material/logo-text.html is used. It does not seem to be included anywhere. It is referenced in examples for html_sidebars, but I can't find how it integrates into the resulting build. Even if I do include it from html_sidebars, I don't manage to find the resulting HTML in _build/. Is this expected?

[Qeole]

Hi, is there anything I can do to help the PR move forward?

[holmboe]

We are also silently affected by this, glad that you found a solution @Qeole 👍