[Docs] Update readme, installation instructions and testing docs

Author: lindyhopchris

README.md

@@ -79,7 +79,8 @@ Join the Laravel JSON:API community on
 
 | Laravel | This Package |
 | --- | --- |
-| `^8.0` | `^3.0` |
+| `^9.0` | `^4.0` |
+| `^8.0` | `^3.0|^4.0` |
 | `^7.0` | `^2.0` |
 | `^6.0` | `^1.7` |
 | `5.8.*` | `^1.7` |

docs/basics/testing.md

@@ -1,3 +1,14 @@
 # Testing
 
-@todo
+## Installation
+
+As per the installation instructions, you can install the test dependency via Composer with the following command:
+
+```bash
+composer require --dev laravel-json-api/testing:^1.1
+```
+
+## Documentation
+
+This testing package has extensive
+[documentation on the laraveljsonapi.io website.](https://laraveljsonapi.io/docs/1.0/testing/)

docs/installation.md

@@ -4,7 +4,7 @@ Install using [Composer](http://getcomposer.org):
 
 ```bash
 $ composer require cloudcreativity/laravel-json-api
-$ composer require --dev "cloudcreativity/json-api-testing"
+$ composer require --dev "laravel-json-api/testing:^1.1"
 ```
 
 This package's service provider and facade will be automatically added using package discovery. You will