Add Progressbar to Milestone Page (#25050)

This is adds the progress bar, which is already on the Milestone List,
also to the Page of a Single Milestone.


![grafik](https://github.com/go-gitea/gitea/assets/15185051/24e0fa28-369b-4bb9-807a-ee823b46ba81)

---------

Co-authored-by: silverwind <me@silverwind.io>

web_src/css/repo.css

@@ -1225,6 +1225,11 @@
   height: 200px;
 }
 
+.milestone-progress-big {
+  width: min(420px, 96vw);
+  height: 10px;
+}
+
 .repository.compare.pull .show-form-container {
   text-align: left;
 }