Add post processing feature to the readme (#4499)

* Add post processing feature to the readme

Adds post processing information to the GPU section in the readme.

* correct "Anti-Aliasing"

README.md

@@ -96,7 +96,7 @@ Ryujinx system files are stored in the `Ryujinx` folder. This folder is located
 
 - **GPU**
 
-  The GPU emulator emulates the Switch's Maxwell GPU using either the OpenGL (version 4.5 minimum), Vulkan, or Metal (via MoltenVK) APIs through a custom build of OpenTK or Silk.NET respectively. There are currently four graphics enhancements available to the end user in Ryujinx: Disk Shader Caching, Resolution Scaling, Aspect Ratio Adjustment, and Anisotropic Filtering. These enhancements can be adjusted or toggled as desired in the GUI.
+  The GPU emulator emulates the Switch's Maxwell GPU using either the OpenGL (version 4.5 minimum), Vulkan, or Metal (via MoltenVK) APIs through a custom build of OpenTK or Silk.NET respectively. There are currently six graphics enhancements available to the end user in Ryujinx: Disk Shader Caching, Resolution Scaling, Anti-Aliasing, Scaling Filters (including FSR), Anisotropic Filtering and Aspect Ratio Adjustment. These enhancements can be adjusted or toggled as desired in the GUI.
 
 - **Input**