Improve the documentation regarding contributions (#3500)

* Document how to contribute with code

* Improve the contribution guides according to code review

CONTRIBUTING.md

@@ -8,6 +8,8 @@ Please read it before you start participating.
 * [Asking Questions](#asking-questions)
 * [Reporting Security Issues](#reporting-security-issues)
 * [Reporting Issues](#reporting-other-issues)
+* [Triage Issues](#triage-issues)
+* [Submitting Pull Requests](#submitting-pull-requests)
 * [Developers Certificate of Origin](#developers-certificate-of-origin)
 * [Code of Conduct](#code-of-conduct)
 
@@ -37,6 +39,19 @@ When reporting issues, please fill out our issue template. The information the t
 
 You can triage issues which may include reproducing bug reports or asking for vital information, such as version numbers or reproduction instructions. If you would like to start triaging issues, one easy way to get started is to [subscribe to alamofire on CodeTriage](https://www.codetriage.com/alamofire/alamofire).
 
+## Submitting Pull Requests
+
+You can contribute by fixing bugs or adding new features. For larger code changes, we first recommend discussing them in our [Github issues](https://github.com/Alamofire/Alamofire/issues) or on our [Swift Forums](https://forums.swift.org/c/related-projects/alamofire/). When submitting a pull request, please add relevant tests and ensure your changes don't break any existing tests (see [Automated Tests](#automated-tests) below).
+
+### Automated Tests
+
+Alamofire's tests depend on our [Firewalk](https://github.com/Alamofire/Firewalk) test server. To run the automated tests, you first need to have the server running locally. 
+
+In your terminal, run the following commands:
+- To install Firewalk: `brew install alamofire/alamofire/firewalk`
+- To run and detach the server: `firewalk &`
+- To stop the server, run `kill` and provide the pid output after launch.
+
 ## Developer's Certificate of Origin 1.1
 
 By making a contribution to this project, I certify that:

README.md

@@ -16,6 +16,7 @@ Alamofire is an HTTP networking library written in Swift.
 - [Migration Guides](#migration-guides)
 - [Communication](#communication)
 - [Installation](#installation)
+- [Contributing](#contributing)
 - [Usage](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#using-alamofire)
     - [**Introduction -**](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#introduction) [Making Requests](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#making-requests), [Response Handling](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#response-handling), [Response Validation](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#response-validation), [Response Caching](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#response-caching)
 	- **HTTP -** [HTTP Methods](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#http-methods), [Parameters and Parameter Encoder](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md##request-parameters-and-parameter-encoders), [HTTP Headers](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#http-headers), [Authentication](https://github.com/Alamofire/Alamofire/blob/master/Documentation/Usage.md#authentication)
@@ -88,7 +89,6 @@ Due to these issues, Alamofire is unsupported on Linux and Windows. Please repor
 - If you'd like to **discuss Alamofire best practices**, use [our forum on swift.org](https://forums.swift.org/c/related-projects/alamofire).
 - If you'd like to **discuss a feature request**, use [our forum on swift.org](https://forums.swift.org/c/related-projects/alamofire). 
 - If you **found a bug**, open an issue here on GitHub and follow the guide. The more detail the better!
-- If you **want to contribute**, submit a pull request!
 
 ## Installation
 
@@ -158,6 +158,10 @@ If you prefer not to use any of the aforementioned dependency managers, you can
 
   > The `Alamofire.framework` is automagically added as a target dependency, linked framework and embedded framework in a copy files build phase which is all you need to build on the simulator and a device.
 
+## Contributing
+
+Before contributing to Alamofire, please read the instructions detailed in our [contribution guide](https://github.com/Alamofire/Alamofire/blob/master/CONTRIBUTING.md).
+
 ## Open Radars
 
 The following radars have some effect on the current implementation of Alamofire.