Update progress info and start welcome info (#3768)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [x] Refactoring

---------

Signed-off-by: jinhai <haijin.chn@gmail.com>

rag/app/presentation.py

@@ -59,11 +59,12 @@ class Pdf(PdfParser):
 
     def __call__(self, filename, binary=None, from_page=0,
                  to_page=100000, zoomin=3, callback=None):
-        callback(msg="OCR is running...")
+        from timeit import default_timer as timer
+        start = timer()
+        callback(msg="OCR started")
         self.__images__(filename if not binary else binary,
                         zoomin, from_page, to_page, callback)
-        callback(0.8, "Page {}~{}: OCR finished".format(
-            from_page, min(to_page, self.total_page)))
+        callback(msg="Page {}~{}: OCR finished ({:.2f}s)".format(from_page, min(to_page, self.total_page), timer() - start))
         assert len(self.boxes) == len(self.page_images), "{} vs. {}".format(
             len(self.boxes), len(self.page_images))
         res = []