update optional pydarshan dependencies

Author: Shane Snyder

darshan-util/pydarshan/RELEASE-CHECKLIST-PyDarshan.txt

@@ -5,7 +5,7 @@ Notes on how to release a new version of PyDarshan
  - Ensure python dev environment with dev dependencies, if not already present
     (- python3 -m venv venv)
     (- source venv/bin/activate)
-    (- pip install -r requirements_dev.txt    # deps for packaging, testing, and docs generation)
+    (- pip install .[dev,test]    # deps for packaging, testing, and docs generation)
 
  - Update CHANGELOG.rst
     - commit

darshan-util/pydarshan/pyproject.toml

@@ -46,6 +46,11 @@ test = [
     "lxml",
     "importlib_resources;python_version<'3.9'",
 ]
+dev = [
+    "sphinx",
+    "sphinx_rtd_theme",
+    "pipx"
+]
 
 [tool.setuptools.packages.find]
 include = ["darshan"]