Enable isort linting rules (#267)

See https://docs.astral.sh/ruff/rules/#isort-i.

src/common/endoflife.py

@@ -1,11 +1,13 @@
-import frontmatter
 import json
 import logging
 import os
 import re
 from datetime import datetime
 from glob import glob
+
+import frontmatter
 from liquid import Template
+
 logging.basicConfig(format=logging.BASIC_FORMAT, level=logging.INFO)
 
 # Handle versions having at least 2 digits (ex. 1.2) and at most 4 digits (ex. 1.2.3.4), with an optional leading "v".