pyproject.toml: Add docs group with sphinx

Add the sphinx package to a separate dependency group.

Signed-off-by: Pieter De Gendt <[email protected]>

Author: pdgendt

pyproject.toml

@@ -56,6 +56,11 @@ dev = [
     {include-group = "test"},
     {include-group = "types"},
 ]
+docs = [
+    "sphinx~=8.1",
+    "sphinx-rtd-theme~=3.0",
+    "sphinx-tabs~=3.4",
+]
 
 [tool.setuptools]
 package-dir = {"" = "src"}