Add installation hint

Author: ctjdr

README.md

@@ -1,11 +1,15 @@
 # Pure Sheet
 
-An eye-friendly light VS Code color scheme based on the [Clean Sheet](https://fappel.github.io/xiliary/clean-sheet.html) theme.
+An eye-friendly light Visual Studio Code color scheme based on the [Clean Sheet](https://fappel.github.io/xiliary/clean-sheet.html) theme.
 
 
 ![Pure Sheet Screenshot](doc/images/pure-sheet-01.png)
 
 
+## Installation
+
+Directly install the "Pure Sheet" extension from Visual Studio Code, or [download from Visual Studio Code Marketplace](https://marketplace.visualstudio.com/items?itemName=ctjdr.pure-sheet).
+
 ## Font
 
 The font used by the original Clean Sheet theme is _[Source Code Pro](https://fonts.google.com/specimen/Source+Code+Pro)_.