Added ASP demo readme file

Author: amusleh-spotware-com

src/ASP.NET.Demo/README.md

@@ -0,0 +1,21 @@
+# ASP.NET.Demo
+
+The ASP demo is a Razor pages web app that allows you to interact with Open API by using the OpenAPI.NET.
+
+To use it you have to create a "appsettings-dev.json" configuration file in project root and write your Open API application credentials on it:
+
+```json
+{
+  "ApiCredentials": {
+    "ClientId": "your-application-client-id",
+    "Secret": "your-application-client-secret"
+  }
+}
+```
+The app will load your Open API application credentials and it will use it.
+
+You have to also add your web app host URL in your API application redirect URIs, otherwise the account authorization will not work and you will get an error.
+
+The application default URL is set to https://localhost:5001/ and http://localhost:5000/, add both to your API application redirect URIs.
+
+You can find the application URL on project/properties/launchSettings.json file, you can change it from there if you want to.