test(samples): add new samples

src/test/resources/test-compile-data/jvm/kotlin-web-site/strings/684a78155560e29c60cfedf300a516a1.6.kt

@@ -1,18 +1,23 @@
 fun main() { 
 //sampleStart
-    // Formats to add zeroes and make a length of seven
+    // Formats an integer, adding leading zeroes to reach a length of seven characters
     val integerNumber = String.format("%07d", 31416)
     println(integerNumber)
     // 0031416
 
-    // Formats with four decimals and sign
+    // Formats a floating-point number to display with a + sign and four decimal places
     val floatNumber = String.format("%+.4f", 3.141592)
     println(floatNumber)
     // +3.1416
 
-    // Formats with uppercase for two placeholders
+    // Formats two strings to uppercase, each taking one placeholder
     val helloString = String.format("%S %S", "hello", "world")
     println(helloString)
     // HELLO WORLD
+
+    // Formats a negative number to be enclosed in parentheses, then repeats the same number in a different format (without parentheses) using `argument_index$`.
+    val negativeNumberInParentheses = String.format("%(d means %1\$d", -31416)
+    println(negativeNumberInParentheses)
+    //(31416) means -31416
 //sampleEnd    
 }