📖 [Docs]: Add docs reference to the GitHub module (#3)

## Description

- Add docs reference to the GitHub module

## Type of change

<!-- Use the check-boxes [x] on the options that are relevant. -->

- [x] 📖 [Docs]
- [ ] 🪲 [Fix]
- [ ] 🩹 [Patch]
- [ ] ⚠️ [Security fix]
- [ ] 🚀 [Feature]
- [ ] 🌟 [Breaking change]

## Checklist

<!-- Use the check-boxes [x] on the options that are relevant. -->

- [x] I have performed a self-review of my own code
- [x] I have commented my code, particularly in hard-to-understand areas

Author: MariusStorhaug

README.md

@@ -2,6 +2,8 @@
 
 A GitHub Action used for running a PowerShell Script that uses the GitHub PowerShell module.
 
+For more information on the available functions and automatic loaded variables, see the [GitHub PowerShell module documentation](https://psmodule.io/GitHub)
+
 ## Usage
 
 ### Inputs