update(packaging): declare plugin compatible with ProperDocs (#431)

See: https://github.com/orgs/ProperDocs/discussions/33

Author: Guts

pyproject.toml

@@ -40,7 +40,8 @@ classifiers = [
 dependencies = [
     "CacheControl[filecache]>=0.14.3,<1",
     "GitPython>=3.1.45,<3.2",
-    "mkdocs>=1.6.1,<2",
+    "mkdocs==1.6.1",
+    "properdocs >=1.6.5,<2",
     "requests>=2.32.5,<3",
     "tzdata>=2024,<2026 ; sys_platform == 'win32'",
 ]