KotlinX Serialization version updated to 0.20.0.

Signed-off-by: Pavel Erokhin (MairwunNx) <MairwunNx@gmail.com>

Author: MairwunNx

gradle.properties

@@ -12,7 +12,7 @@ brigadier_version=1.0.17
 kotlin_jdk_version_target=jdk8
 project_jvm_version_target=1.8
 kotlin_version=1.3.70
-kotlinx_serialization_version=0.14.0
+kotlinx_serialization_version=0.20.0
 module_version=1.14.4-1.1.1
 module_name=Project Essentials Chat
 module_id=project_essentials_chat