Extend checks to folder names

.github/workflows/validate.yaml

@@ -77,7 +77,7 @@ jobs:
             exit 1
           fi
 
-      - name: Check file names
+      - name: Check file and folder names in content
         shell: python {0}
         continue-on-error: true
         run: |
@@ -93,15 +93,17 @@ jobs:
           for root, dirs, files in os.walk(content_dir):
             for file in files:
               full_path = Path(root, file)
-              if full_path.suffix.lower() != '.md':
-                continue
               if full_path.name == '_index.md':
                 continue
               if not allowed_chars.match(full_path.stem):
                 errors.append(f"- {full_path}'\n")
+
+            for dir in dirs:
+              if not allowed_chars.match(dir):
+                errors.append(f"- {Path(root, dir)}'\n")
           
           if len(errors) > 0:
-            print("The following file names use invalid characters. Only lowercase letters, digits, hyphens and period are allowed.\n\n")
+            print("The following file/folder names use invalid characters. Only lowercase letters, digits, hyphens and period are allowed.\n\n")
             for error in errors:
               print(error)
             sys.exit(1)