Add ITP for markdownlint

Author: jwilk

data/markdown.ini

@@ -1,3 +1,3 @@
 # TODO: https://github.com/shurcooL/markdownfmt
-# TODO: https://github.com/markdownlint/markdownlint
+# TODO: https://github.com/markdownlint/markdownlint (https://bugs.debian.org/1026114)
 # TODO: https://github.com/igorshubovych/markdownlint-cli