Implement CharSequence.isEmpty method in stdlib.js. Remove corresponding intrinsic.

js/js.libraries/src/core/string.kt

@@ -48,8 +48,6 @@ native public fun String.match(regex : String) : Array<String> = noImpl
 native("length")
 public val CharSequence.size: Int get() = noImpl
 
-library
-public fun CharSequence.isEmpty(): Boolean = noImpl
 
 
 

js/js.libraries/src/core/stringsCode.kt

@@ -43,6 +43,7 @@ public inline fun String.matches(regex : String) : Boolean {
     return result != null && result.size() > 0
 }
 
+public inline fun CharSequence.isEmpty(): Boolean = this.length() == 0
 
 public fun String.isBlank(): Boolean = length() == 0 || matches("^[\\s\\xA0]+$")