Add keymap-drawer workflow

I haven't tuned the output. For now this is just a demonstration of the
workflow.

Justfile

@@ -4,6 +4,7 @@ default:
 config := absolute_path('config')
 build := absolute_path('.build')
 out := absolute_path('firmware')
+draw := absolute_path('draw')
 
 # parse combos.dtsi and adjust settings to not run out of slots
 _parse_combos:
@@ -75,6 +76,13 @@ clean:
 clean-nix:
     nix-collect-garbage --delete-old
 
+# parse & plot keymap
+draw:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    keymap -c "{{ draw }}/config.yaml" parse -z "{{ config }}/base.keymap" >"{{ draw }}/base.yaml"
+    keymap -c "{{ draw }}/config.yaml" draw "{{ draw }}/base.yaml" -k "ferris/sweep" >"{{ draw }}/base.svg"
+
 # initialize west
 init:
     west init -l config