Update README.md

Author: augustdominik

README.md

@@ -7,6 +7,8 @@
   1. Open package manager
   2. Add package from git URL
   3. Paste: https://github.com/GucioDevs/SimpleMinMaxSlider.git#upm (remember the #upm at the end)
+  4. Let Unity do its thing
+  5. Done.
 
 # Usage