Comment for bingen backwards-compat field ordering

pkg/kubecost/bingen.go

@@ -1,5 +1,25 @@
 package kubecost
 
+////////////////////////////////////////////////////////////////////////////////
+// NOTE: If you add fields to _any_ struct that is serialized by bingen, please
+// make sure to add those fields to the END of the struct definition. This is
+// required for backwards-compatibility. So:
+//
+// type Foo struct {
+//     ExistingField1 string
+//     ExistingField2 int
+// }
+//
+// becomes:
+//
+// type Foo struct {
+//     ExistingField1 string
+//     ExistingField2 int
+//     NewField       float64 // @bingen: <- annotation ref: bingen README
+// }
+//
+////////////////////////////////////////////////////////////////////////////////
+
 // Default Version Set (uses -version flag passed) includes shared resources
 // @bingen:generate:Window