add comment explaining harcoded example

Cargo.toml

@@ -67,7 +67,7 @@ vcr-cassette = "2.0.1"
 harness = false # allows Cucumber to print output instead of libtest
 name = "main"
 
-[[example]]
+[[example]] # signal to Cargo that dev-dependencies are allowed for examples
 doc-scrape-examples = true
 name="v1_authentication_validate"