add: Add docs dependency group in pyproject.toml

Author: DhavalGojiya

docs/requirements.txt

@@ -67,6 +67,10 @@ dev = [
   "time-machine>=2.19",
   "types-croniter>=6.0.0.20250411",
 ]
+docs = [
+  "mkdocs>=1.6.1",
+  "mkdocs-material>=9.7.4",
+]
 
 [tool.hatch.build.targets.sdist]
 include = [ "scheduler" ]