add diff function

kibot.yaml

@@ -232,6 +232,38 @@ outputs:
       output: '%f-report.%x'
       do_convert: true
 
+  # Schematic diff
+  - name: 'sch_diff'
+    comment: "Schematic diff PDF"
+    type: diff
+    dir: DIFF
+    disabled_by_default: false
+    options:
+      output: '%f-schematic-diff.%x'
+      format: PDF
+      diff_mode: 'red_green'
+      old: 'HEAD~1'
+      new: 'HEAD'
+      cache_dir: '.cache'
+      add_link_id: true
+      only_different: true
+      
+  # PCB diff  
+  - name: 'pcb_diff'
+    comment: "PCB diff PDF"
+    type: diff
+    dir: DIFF
+    disabled_by_default: false
+    options:
+      output: '%f-pcb-diff.%x'
+      format: PDF
+      diff_mode: 'red_green'
+      old: 'HEAD~1'
+      new: 'HEAD'
+      cache_dir: '.cache'
+      pcb: true
+      only_different: true
+
   # JLCPCB fabrication package
   - name: 'jlcpcb_gerbers'
     comment: "Gerbers for JLCPCB"