docs: adds CHANGELOG entry for #44

Signed-off-by: Matthew Weier O'Phinney <matthew@weierophinney.net>

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release.
 
-## 2.3.1 - TBD
+## 2.3.1 - 2020-07-07
 
 ### Added
 
@@ -22,7 +22,7 @@ All notable changes to this project will be documented in this file, in reverse
 
 ### Fixed
 
-- Nothing.
+- [#44](https://github.com/laminas/laminas-diactoros/pull/44) fixes an issue whereby the uploaded file size was being provided as an integer string, and causing type errors. The value is now cast to integer before creating an `UploadedFile` instance.
 
 ## 2.3.0 - 2020-04-27