[csharp] add missing anchor tags in readme (#4019)

modules/swagger-codegen/src/main/resources/csharp/README.mustache

@@ -16,6 +16,7 @@ This C# SDK is automatically generated by the [Swagger Codegen](https://github.c
     For more information, please visit [{{{infoUrl}}}]({{{infoUrl}}})
 {{/infoUrl}}
 
+<a name="frameworks-supported"></a>
 ## Frameworks supported
 {{^supportUWP}}
 - .NET 4.0 or later
@@ -25,6 +26,7 @@ This C# SDK is automatically generated by the [Swagger Codegen](https://github.c
 - UWP
 {{/supportUWP}}
 
+<a name="dependencies"></a>
 ## Dependencies
 - [RestSharp](https://www.nuget.org/packages/RestSharp) - 105.1.0 or later
 - [Json.NET](https://www.nuget.org/packages/Newtonsoft.Json/) - 7.0.0 or later
@@ -37,6 +39,7 @@ Install-Package Newtonsoft.Json
 
 NOTE: RestSharp versions greater than 105.1.0 have a bug which causes file uploads to fail. See [RestSharp#742](https://github.com/restsharp/RestSharp/issues/742)
 
+<a name="installation"></a>
 ## Installation
 Run the following command to generate the DLL
 - [Mac/Linux] `/bin/sh build.sh`
@@ -48,7 +51,7 @@ using {{packageName}}.{{apiPackage}};
 using {{packageName}}.Client;
 using {{packageName}}.{{modelPackage}};
 ```
-
+<a name="getting-started"></a>
 ## Getting Started
 
 ```csharp
@@ -124,6 +127,7 @@ Class | Method | HTTP request | Description
 No model defined in this package
 {{/modelPackage}}
 
+<a name="documentation-for-authorization"></a>
 ## Documentation for Authorization
 
 {{^authMethods}}