Update CONTRIBUTORS.md

adding Paweł Haracz contribution

CONTRIBUTORS.md

@@ -479,6 +479,7 @@ We will be listing contributors in alphabetical order, by week, by challenge. At
 - [Barbara Forbes](https://github.com/Ba4bes/25daysofserverless/tree/master/Daya24Gavlebocken) - `Logic App, Sentiment Analysis`
 - [Marcus Turewicz](https://github.com/marcusturewicz/25-days-of-serverless-challenge/tree/master/Day-24) - `C# Azure Function, Key Vault, Managed Identity and Twitter webhooks`
 - [Stuart Leaver](https://github.com/stuartleaver/25-days-of-serverless/tree/master/24-security-and-integrity) - `C#, Logic App, CosmosDB, Azure Functions, Translation and Sentiment Analysis, App Service for the UI, Azure Key Vault.`
+- [Paweł Haracz](https://github.com/PawelHaracz/25daysofserverless/tree/master/Day24) - `Azure KeyVault, Facebook Authentication`
 
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