Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
there is no direct tutorial to create a website like tinyurlwebsite.com
but you can follow this article
and you can create your own version by using Azure services like Azure Functions, Azure Cosmos DB for NoSQL database, and Azure API Management for APIs. Azure Functions can be triggered by events to generate short URLs, while Azure Cosmos DB stores the original URL, hash, and other required data. Azure API Management would be used for handling API requests.
Also the following training can help you to better understands the relevant services