feat(sterni/mblog): add package to read maildirs

Change-Id: I7be8d8b7d12bb194712aa26f3ddad74340357779
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5070
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

users/sterni/mblog/packages.lisp

@@ -1,3 +1,10 @@
+(defpackage :maildir
+  (:use :common-lisp)
+  (:shadow :list)
+  (:export :list)
+  (:documentation
+   "Very incomplete package for dealing with maildir(5)."))
+
 (defpackage :mblog
   (:use
    :common-lisp