fix: Correct the formatting of Milliseconds to be a 3-digit number (#126

)

```release-note
修复重命名模板中 millisecond 没有被格式化3位数的问题
```

src/main/java/run/halo/s3os/PlaceholderReplacer.java

@@ -69,7 +69,7 @@ private static String generateRandomNumber(String[] placeholderParams) {
 
  private static String currentMillisecond(Map<String, String> reusableParams) {
  LocalDateTime time = LocalDateTime.parse(reusableParams.get("time"));
- return String.valueOf(time.getNano() / 1000000);
+ return String.format("%03d", time.getNano() / 1000000);
  }
 
  private static String currentSecond(Map<String, String> reusableParams) {