Update Release Notes

Author: matthias-wende-frequenz

RELEASE_NOTES.md

@@ -27,6 +27,7 @@
   - Provide access to `capacity` (maximum number of elements) in `MovingWindow`.
   - Methods to retrieve oldest and newest timestamp of valid samples are added to both.
 
+- A tutorial section and a getting started tutorial
 
 - Now when printing `FormulaEngine` for debugging purposes the the formula will be shown in infix notation, which should be easier to read.