Add sphinx-reredirects to handle redirects

- For example, installation.html now redirects to installation/index.html

docs/conf.py

@@ -36,6 +36,7 @@ extensions = [
     "sphinx_inline_tabs",
     "sphinx_removed_in",
     "sphinxext.opengraph",
+    "sphinx_reredirects",
 ]
 
 intersphinx_mapping = {"python": ("https://docs.python.org/3", None)}
@@ -350,3 +351,8 @@ ogp_image = (
     "pillow-logo-dark-text-1280x640.png"
 )
 ogp_image_alt = "Pillow"
+
+# sphinx-reredirects
+redirects = {
+     "installation.html": "installation/index.html"
+}

pyproject.toml

@@ -47,6 +47,7 @@ docs = [
   "sphinx-inline-tabs",
   "sphinx-removed-in",
   "sphinxext-opengraph",
+  "sphinx-reredirects",
 ]
 fpx = [
   "olefile",