Add lint rule for todo

.github/config.yml

@@ -5,3 +5,4 @@ todo:
   autoAssign: true                        # string|string[]|boolean
   label: ["todo"]                         # boolean|string|string[]
   reopenClosed: true                      # boolean
+  exclude: ".*lint\\.yaml|.*/(zzz_generated|zap-generated)/.*" # string

.github/workflows/lint.yml

@@ -41,3 +41,8 @@ jobs:
       - name: Check for incorrect error use in VerifyOrExit
         run: |
           git grep -n "VerifyOrExit(.*, [A-Za-z]*_ERROR" -- './*' ':(exclude).github/workflows/lint.yml' && exit 1 || exit 0
+
+      # Comments like '{{! ... }}' should be used in zap files
+      - name: Do not allow TODO in generated files
+        run: |
+          git grep -n 'TODO:' -- ./zzz_generated './*/zap-generated/*' && exit 1 || exit 0

src/app/zap-templates/templates/app/CHIPClientCallbacks-src.zapt

@@ -118,9 +118,9 @@ namespace {
     }
 
 
-// TODO: These IM related callbacks contains small or no generated code, should be put into seperate file to reduce the size of template.
-// Singleton instance of the callbacks manager
+{{! TODO: These IM related callbacks contains small or no generated code, should be put into seperate file to reduce the size of template. }}
 
+// Singleton instance of the callbacks manager
 app::CHIPDeviceCallbacksMgr & gCallbacks = app::CHIPDeviceCallbacksMgr::GetInstance();
 
 {{#chip_client_clusters}}