docs: init c4 diagrams

docs/mkdocs.yml

@@ -10,19 +10,19 @@ validation:
   unrecognized_links: warn
 
 markdown_extensions:
+  - admonition
   - attr_list
+  - footnotes
+  - meta
+  - plantuml_markdown
   - pymdownx.emoji:
       emoji_index: !!python/name:material.extensions.emoji.twemoji
       emoji_generator: !!python/name:material.extensions.emoji.to_svg
-
   - pymdownx.tasklist:
       custom_checkbox: true
   - pymdownx.superfences
   - pymdownx.tabbed:
       alternate_style: true
-  - footnotes
-  - meta
-  - admonition
   - pymdownx.details
   - pymdownx.highlight:
       use_pygments: true

docs/nix/default.nix

@@ -1,11 +1,17 @@
 { pkgs, module-docs, ... }:
+let
+  uml-c4 = pkgs.python3Packages.plantuml-markdown.override { plantuml = pkgs.plantuml-c4; };
+in
 pkgs.stdenv.mkDerivation {
   name = "clan-documentation";
 
   src = ../.;
 
   nativeBuildInputs =
-    [ pkgs.python3 ]
+    [
+      pkgs.python3
+      uml-c4
+    ]
     ++ (with pkgs.python3Packages; [
       mkdocs
       mkdocs-material