feat(users/sterni/mblog): implement mblog executable

This change finally sort of puts the parts together: We take a maildir,
render all its note messages as standalone HTML, extract the attachments
alongside and finally generate a global index page linking all notes.

The new executable and mnote-html are both contained in the same image
and we dispatch the right functionality based on argv[0].

Change-Id: I5a5bdbfaca79199f92e73ea4a2f070fa900d2bc4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5113
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

users/sterni/mblog/packages.lisp

@@ -32,6 +32,20 @@
 (defpackage :mblog
   (:use
    :common-lisp
-   :uiop
+   :klatre
+   :who
+   :maildir
    :note)
+  (:export :build-mblog)
+  (:import-from :local-time :universal-to-timestamp)
+  (:import-from :sclf :pathname-as-directory)
+  (:shadowing-import-from :common-lisp :list))
+
+(defpackage :cli
+  (:use
+   :common-lisp
+   :uiop
+   :note
+   :mblog)
+  (:import-from :alexandria :starts-with)
   (:export :main))