Updated changelog.

See #3617

Author: mp911de

src/main/resources/changelog.txt

@@ -1,6 +1,13 @@
 Spring Data MongoDB Changelog
 =============================
 
+Changes in version 3.1.8 (2021-04-14)
+-------------------------------------
+* #3623 - `@Aggregation` repository query method causes `NullPointerException` when the result is empty.
+* #3601 - Criteria object not allowing to use field names with underscore in them.
+* #3414 - Criteria or toEquals fail if contains regex [DATAMONGO-2559].
+
+
 Changes in version 3.0.9.RELEASE (2021-04-14)
 ---------------------------------------------
 * #3623 - `@Aggregation` repository query method causes `NullPointerException` when the result is empty.
@@ -3411,5 +3418,6 @@ Repository
 
 
 
+