Upgrade kotlinx.html

Author: Sergey Mashkov

build.gradle

@@ -20,7 +20,7 @@ subprojects { p ->
 
 subprojects {
     ext.kotlin_version = "1.1.51"
-    ext.html_version = "0.6.4"
+    ext.html_version = "0.6.6"
     ext.ktor_version = "0.3.0"
     ext.squash_version = "0.2.2"