Update README

README.md

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-Description
+# 📝 What is ReceiptVerifierMiddlewareEndpoint?
+
+ReceiptVerifierMiddlewareEndpoint is a library used to add an endpoint to verify and get information about receipt from Apple. It uses [AppleReceiptVerifier.NET](https://github.com/alexalok/AppleReceiptVerifier.NET) to get information from Apple.
+
+## Installation
+
+Use the package manager [NuGet](https://www.nuget.org/packages/ReceiptVerifierMiddlewareEndpoint) to install library.
+
+```bash
+NuGet\Install-Package ReceiptVerifierMiddlewareEndpoint -Version 1.0.1
+```
+
+## ⚙️  Configuration
+Before beginning please make sure you injected AppleReceiptVerifier.NET to your project. Otherwise you will get an exception.
+
+Firstly use AddReceiptVerifierEndpointMiddleware method and pass path. You will be able to get receipt info by using that path.
+```csharp
+services.AddReceiptVerifierEndpointMiddleware(op =>
+{
+    op.Path = "/api/Subscriptions/receiptInfo";
+});
+```
+Then call UseReceiptVerifierEndpointMiddleware.
+```csharp
+app.UseReceiptVerifierEndpointMiddleware();
+```
+
+## ℹ️ Usage
+Execute GET request on path you set in configuration. Body of request must contain valid receipt.
+```json
+{
+    "receipt" : "very long base64encoded string"
+}
+```