Mention that mardkownlint does not check ol indentation (openxla#940)

.markdownlint.yaml

@@ -19,10 +19,14 @@
 default: true
 
 # List formatting:
+#
 # 1. Lists must have a blank line before AND after the list.
 # 2. Lists start aligned to the left (do not indent the top level list items).
+#    NOTE: markdownlint currently checks indentation for unordered lists only.
+#          Please manually verify that your ordered lists are not indented.
+#          See https://github.com/DavidAnson/markdownlint/issues/138.
 # 3. You may use one or zero blank lines between list items.
-# 4. Nested list items must be indented to align with the first character of
+# 4. Nested list items should be indented to align with the first character of
 #    the first line. For bullet lists, that means 2 spaces. For numbered
 #    lists, that's 3 spaces (but 4 spaces is okay if that's easier).
 # 5. In multiline list items, subsequent lines are indented by 2 spaces.