[Diff][Added] Example for 2color mode

tests/yaml_samples/diff_file_2color_k7.kibot.yaml

@@ -0,0 +1,16 @@
+kibot:
+  version: 1
+
+outputs:
+  - name: 'diff_pcb'
+    comment: "PCB difference with reference file (KiCad 7)"
+    type: diff
+    layers: ['F.Cu', 'In1.Cu']
+    options:
+      old: tests/board_samples/kicad_7/light_control.kicad_pcb
+      old_type: file
+      cache_dir: .cache
+      diff_mode: 2color
+      color_added: "#3030FF"
+      color_removed: "#FF3030"
+      # zones: unfill