code: @Override
      public FastStr replace(CharSequence target, CharSequence replacement) {
          return unsafeOf(Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
                  this).replaceAll(Matcher.quoteReplacement(replacement.toString())));
      }
docs: Wrapper of {@link String#replace(CharSequence, CharSequence)} but return FastStr type instance
  
  @param target the char sequence to be replaced
  @param replacement the char sequence used to replace {@code target}
  @return a FastStr instance with all {@code target} being replaced with
  {@code replacement}