[#4262] Added date and time to a stamp (#4431)

# Description of Changes

Changed `addTextStamp` method to automatically add time and date when
stamping a file

Closes #4262 
---

## Checklist

### General

- [✓] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [✓] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [✓] I have performed a self-review of my own code
- [✓] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

app/core/src/main/java/stirling/software/SPDF/controller/api/misc/StampController.java

@@ -7,6 +7,9 @@ import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.time.LocalDate;
+import java.time.LocalTime;
+import java.time.format.DateTimeFormatter;
 import java.util.List;
 
 import javax.imageio.ImageIO;
@@ -247,6 +250,17 @@ public class StampController {
                     calculatePositionY(
                             pageSize, position, calculateTextCapHeight(font, fontSize), margin);
         }
+
+        String currentDate = LocalDate.now().toString();
+        String currentTime = LocalTime.now().format(DateTimeFormatter.ofPattern("HH:mm:ss"));
+
+        int pageCount = document.getNumberOfPages();
+
+        String processedStampText = stampText
+            .replace("@date", currentDate)
+            .replace("@time", currentTime)
+            .replace("@page_count", String.valueOf(pageCount));
+
         // Split the stampText into multiple lines
         String[] lines =
                 RegexPatternUtils.getInstance().getEscapedNewlinePattern().split(stampText);