updated changelog and readme for version 5.2.1

Author: Zhihang Yao

CHANGES.md

@@ -1,10 +1,12 @@
 Change Log
 ==========
 
-### 5.2.1 -tba
+### 5.2.1 - 2022-07-29
 
 #### Fixes
-*  Fixed XXE vulnerabilities when parsing XML files. [#258](https://github.com/3dcitydb/importer-exporter/pull/258)
+* Fixed XXE vulnerabilities when parsing XML files. [#258](https://github.com/3dcitydb/importer-exporter/pull/258)
+* Fixed connection timeout issue in CityGML exports. [#263](https://github.com/3dcitydb/importer-exporter/pull/263)
+* Fixed building of queries requiring `SELECT DISTINCT` statement. [#264](https://github.com/3dcitydb/importer-exporter/pull/264)
 
 ### 5.2.0 - 2022-05-23
 

README.md

@@ -47,9 +47,9 @@ previous release of the 3D City Database Importer/Exporter under Apache License
 
 Latest release
 --------------
-The latest stable release of the 3D City Database Importer/Exporter is 5.2.0.
+The latest stable release of the 3D City Database Importer/Exporter is 5.2.1.
 
-Download the software [here](https://github.com/3dcitydb/importer-exporter/releases/download/v5.2.0/3DCityDB-Importer-Exporter-5.2.0.zip).
+Download the software [here](https://github.com/3dcitydb/importer-exporter/releases/download/v5.2.1/3DCityDB-Importer-Exporter-5.2.1.zip).
 Previous releases are available from the [releases section](https://github.com/3dcitydb/importer-exporter/releases).
 
 System requirements