added package manager install instructions

Author: Chris Handzlik

README.md

@@ -18,7 +18,9 @@ Works with any code editor.
 
 ## Quickstart
 1) Download [latest FSR version](https://github.com/handzlikchris/FastScriptReload/releases/download/1.4-rc1/Fast.Script.Reload.unitypackage) and import to Unity
-2) Play
+> You can also install via package manager. Window -> Package Manager -> + -> Add package from Git url:
+> https://github.com/handzlikchris/FastScriptReload?path=Assets
+3) Play
 3) Make Code Change
 4) See results