update readme - add installation section

README.md

@@ -1,5 +1,11 @@
 # Death Counter
 
-A simple counter clock to your death screensaver for macOS.
+A very simple clock counter screensaver that counts to your death.
 
 ![screenshot](preview.png)
+
+## Installation
+
+- Download the [latest version](https://github.com/anhmv/DeathCounter/releases/latest) of the screensaver from the releases page.
+- Extract the ZIP file by double-clicking on it.
+- Install the screensaver by double-clicking on the file with the extension `.saver`.