Added initial Hangfire Background Job Manager doc

docs/en/Background-Jobs-Hangfire.md

@@ -1,3 +1,43 @@
 # Hangfire Background Job Manager
 
-TODO
+[Hangfire](https://www.hangfire.io/) is an advanced background job manager. You can integrate Hangfire with the ABP Framework to use it instead of the [default background job manager](Background-Jobs.md). In this way, you can use the same background job API for Hangfire and your code will be independent of Hangfire. If you like, you can directly use Hangfire's API, too.
+
+> See the [background jobs document](Background-Jobs.md) to learn how to use the background job system. This document only shows how to install and configure the Hangfire integration.
+
+## Installation
+
+It is suggested to use the [ABP CLI](CLI.md) to install this package.
+
+### Using the ABP CLI
+
+Open a command line window in the folder of the project (.csproj file) and type the following command:
+
+````bash
+abp add-package Volo.Abp.BackgroundJobs.HangFire
+````
+
+### Manual Installation
+
+If you want to manually install;
+
+1. Add the [Volo.Abp.BackgroundJobs.HangFire](https://www.nuget.org/packages/Volo.Abp.BackgroundJobs.HangFire) NuGet package to your project:
+
+   ````
+   Install-Package Volo.Abp.BackgroundJobs.HangFire
+   ````
+
+2. Add the `AbpBackgroundJobsHangfireModule` to the dependency list of your module:
+
+````csharp
+[DependsOn(
+    //...other dependencies
+    typeof(AbpBackgroundJobsHangfireModule) //Add the new module dependency
+    )]
+public class YourModule : AbpModule
+{
+}
+````
+
+## Configuration
+
+TODO...