Update version code and name in build.gradle.kts to 16 and 2.6 respectively for the upcoming release.

app/build.gradle.kts

@@ -16,8 +16,8 @@ android {
         applicationId = "com.arklan.weather"
         minSdk = ConfigData.minSdk
         targetSdk = ConfigData.targetSdk
-        versionCode = 15
-        versionName = "2.5"
+        versionCode = 16
+        versionName = "2.6"
         setProperty("archivesBaseName", "weekly-weather-v$versionName.$versionCode")
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"