update libcasm-xtal favicons

doc_requirements.txt

@@ -1,7 +1,6 @@
 numpydoc
 sphinx
 sphinx-argparse
-sphinx-favicon
 sphinx_rtd_theme
 sphinxcontrib-bibtex
 pydata-sphinx-theme

python/doc/conf.py

@@ -73,7 +73,6 @@
     "sphinx.ext.viewcode",
     "sphinx.ext.githubpages",
     "sphinx.ext.napoleon",
-    "sphinx_favicon",
     "sphinxarg.ext",
     "sphinxcontrib.bibtex",
     "sphinx.ext.intersphinx",
@@ -163,14 +162,25 @@
             "type": "fontawesome",
         },
     ],
+    "favicons": [
+        {
+            "rel": "icon",
+            "sizes": "32x32",
+            "href": "favicon-32x32.png",
+        },
+        {
+            "rel": "icon",
+            "sizes": "16x16",
+            "href": "favicon-16x16.png",
+        },
+        {"rel": "apple-touch-icon", "sizes": "180x180", "href": "apple-touch-icon.png"},
+    ],
     # "primary_sidebar_end": ["primary_sidebar_end"]
 }
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ["_static"]
-html_favicon = "_static/small_logo.svg"
-favicons = ["small_logo.svg"]
 html_css_files = [
     "css/custom.css",
 ]