fix: Update CHANGELOG.md to include elo evaluation how to

TASK: IL-502

CHANGELOG.md

@@ -10,6 +10,7 @@
  - Add `EloQaEvaluationLogic` for Elo evaluation of QA runs, with optional later addition of more runs to an existing evaluation.
  - Add `EloAggregationAdapter` class to simplify using the `ComparisonEvaluationAggregationLogic` for different Elo use cases.
  - Add `elo_qa_eval` tutorial notebook describing the use of an (incremental) Elo evaluation use case for QA models.
+ -  Add `how_to_implement_elo_evaliations` how to as skeleton for implementing elo evaluation cases
 ### Fixes
 - `ExpandChunks`-task is now fast even for very large documents