Install instructions for Windows Store version

Updated installation instructions with info on where to put the DLL when running the Windows Store version of Paint.NET.

Author: tormodfj

README.md

@@ -10,5 +10,6 @@ Tested on Paint.NET 4.0.13.
 Please check the [Releases](https://github.com/otuncelli/Scalable-Vector-Graphics-Plugin-for-Paint.NET/releases) section for binary download.
 
 To install the plugin perform the following steps:
- * Put the DLL in the <Paint.NET>/FileTypes directory (default location is C:\Program Files\paint.net\FileTypes)
- * Restart Paint.NET if you have it open
+ * Put the DLL in the `<Paint.NET>\FileTypes` directory (default location is `C:\Program Files\paint.net\FileTypes`)
+   * For the [Windows Store version of Paint.NET](https://www.microsoft.com/store/apps/9NBHCS1LX4R0), put the DLL in the `<Documents>\paint.net App Files\FileTypes` directory
+ * Restart Paint.NET if you have it open