ui: Add a progress bar indicating total number of flags

frontend/ui/src/components/ExerciceFlags.svelte

@@ -8,6 +8,7 @@
      Icon,
      ListGroup,
      ListGroupItem,
+     Progress,
      Spinner,
  } from 'sveltestrap';
 
@@ -97,6 +98,16 @@
         <Icon name="flag-fill" />
         Faire son rapport
     </CardHeader>
+    {#if exercice.flags.length != exercice.nb_flags}
+        <Progress
+            value={exercice.flags.length}
+            max={exercice.nb_flags}
+            class="rounded-0"
+            barClassName="text-light"
+        >
+            {exercice.flags.length}/{exercice.nb_flags}
+        </Progress>
+    {/if}
     {#if exercice.tries || exercice.submitted || sberr}
         <ListGroup>
             {#if exercice.solved_time && exercice.tries}