docs: style fixes for api reference docs (#21602)

- Make sure the left nav bar is horizontally scrollable 
- Make sure the navigation dropdown is vertically scrollable and height
capped at 80% of viewport height

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

docs/api_reference/_static/css/custom.css

@@ -12,7 +12,8 @@ pre {
   }
 }
 
-#my-component-root *, #headlessui-portal-root * {
+#my-component-root *,
+#headlessui-portal-root * {
   z-index: 10000;
 }
 

docs/api_reference/create_api_rst.py

@@ -359,9 +359,14 @@ def main(dirs: Optional[list] = None) -> None:
         dirs = [
             dir_
             for dir_ in os.listdir(ROOT_DIR / "libs")
-            if dir_ not in ("cli", "partners")
+            if dir_ not in ("cli", "partners", "standard-tests")
+        ]
+        dirs += [
+            dir_
+            for dir_ in os.listdir(ROOT_DIR / "libs" / "partners")
+            if os.path.isdir(dir_)
+            and "pyproject.toml" in os.listdir(ROOT_DIR / "libs" / "partners" / dir_)
         ]
-        dirs += os.listdir(ROOT_DIR / "libs" / "partners")
     for dir_ in dirs:
         # Skip any hidden directories
         # Some of these could be present by mistake in the code base

docs/api_reference/themes/scikit-learn-modern/static/css/theme.css

@@ -1398,3 +1398,20 @@ table.sk-sponsor-table td {
 .highlight .vi { color: #bb60d5 } /* Name.Variable.Instance */
 .highlight .vm { color: #bb60d5 } /* Name.Variable.Magic */
 .highlight .il { color: #208050 } /* Literal.Number.Integer.Long */
+
+/** Custom styles overriding certain values */
+
+div.sk-sidebar-toc-wrapper {
+  width: unset;
+  overflow-x: auto;
+}
+
+div.sk-sidebar-toc-wrapper > [aria-label="rellinks"] {
+  position: sticky;
+  left: 0;
+}
+
+.navbar-nav .dropdown-menu {
+  max-height: 80vh;
+  overflow-y: auto;
+}