html_report: add report generation timestamp

Ref: ossf#468

src/fuzz_introspector/html_report.py

@@ -21,6 +21,7 @@
 import bs4
 import random
 import string
+from datetime import datetime
 import matplotlib.pyplot as plt
 
 from matplotlib.patches import Rectangle
@@ -840,6 +841,7 @@ def create_html_report(
     # Start creation of core html
     html_body_start = '<div class="content-section">'
     html_overview = "<div class=\"report-box\">"
+    html_overview += "<b>Report generation date:</b>" + datetime.today().strftime('%Y-%m-%d %H:%M:%S') + "<pr>"
     html_overview += html_helpers.html_add_header_with_link(
         f"Project overview: {report_name}",
         1,