Add readme for the DI package and add one more extensions (#2320)

Author: alexeyzimarev

src/RestSharp.Extensions.DependencyInjection/README.md

@@ -0,0 +1,45 @@
+# About
+
+The `RestSharp.Extensions.DependencyInjection` library provides integration with `Microsoft.Extensions.DependencyInjection` components as well as integrates with `IHttpClientFactory`.
+
+# How to use
+
+Use the extension method provided by the package to configure the client:
+
+```csharp
+// Add a default client with no base URL, with default options
+services.AddRestClient(); 
+
+// Add a client with a base URL
+services.AddRestClient(new Uri("https://example.com")); 
+
+// Add a client with a base URL and custom options
+services.AddRestClient(options => 
+{
+    options.BaseUrl = new Uri("https://example.com");
+    options.Timeout = TimeSpan.FromSeconds(30);
+}); 
+```
+
+When the above registrations are used, the `IRestClient` interface can be injected into any class.
+
+In addition, the package supports registering named clients:
+
+```csharp
+services.AddRestClient("my-client", options => 
+{
+    options.BaseUrl = new Uri("https://example.com");
+    options.Timeout = TimeSpan.FromSeconds(30);
+}); 
+```
+
+When the above registrations are used, resolving the client instance should be done using the `IRestClientFactory`:
+
+```csharp
+public class MyClass(IRestClientFactory restClientFactory)
+{
+    IRestClient client = restClientFactory.CreateClient("my-client");
+
+    // Use the client in your code
+}
+```

src/RestSharp.Extensions.DependencyInjection/RestSharp.Extensions.DependencyInjection.csproj

@@ -5,4 +5,10 @@
     <ItemGroup>
       <ProjectReference Include="..\RestSharp\RestSharp.csproj" />
     </ItemGroup>
+    <ItemGroup>
+      <None Update="README.md">
+        <Pack>true</Pack>
+        <PackagePath>/</PackagePath>
+      </None>
+    </ItemGroup>
 </Project>

src/RestSharp.Extensions.DependencyInjection/ServiceCollectionExtensions.cs

@@ -77,6 +77,16 @@ public void AddRestClient(RestClientOptions options) {
             services.AddRestClient(Constants.DefaultRestClient, o => o.CopyFrom(options));
         }
 
+        /// <summary>
+        /// Adds a RestClient to the service collection with custom options.
+        /// </summary>
+        /// <param name="configureRestClient">Function to configure the RestClient options.</param>
+        [PublicAPI]
+        public void AddRestClient(ConfigureRestClient configureRestClient) {
+            Ensure.NotNull(configureRestClient, nameof(configureRestClient));
+            services.AddRestClient(Constants.DefaultRestClient, configureRestClient);
+        }
+
         /// <summary>
         /// Adds a named RestClient to the service collection with base URL.
         /// </summary>