Show offline participants on public scoreboard + filter

app/views/contests/_selectors.html.slim

@@ -0,0 +1,45 @@
+javascript:
+  function updateParams() {
+    categorySelectEl = document.getElementById('categories');
+    offlineInputEl = document.getElementById('offline');
+    if (categorySelectEl && !offlineInputEl) {
+      window.location.replace(`/public/#{@contest.slug}?category=${categorySelectEl.value}`);
+    } else if (!categorySelectEl) {
+      window.location.replace(`/public/#{@contest.slug}?hide_offline=${offlineInputEl.checked}`);
+    } else {
+      window.location.replace(`/public/#{@contest.slug}?category=${categorySelectEl.value}&hide_offline=${offlineInputEl.checked}`);
+    }
+  }
+- if @contest.categories.size > 0
+  .row
+    .col
+      select.mb-2 id="categories" style="padding: 5px"
+        option value=-1
+          = t("contests.scoreboard.all_categories")
+        - @contest.categories.each do |category|
+          option value=category.id
+            = category.name
+      javascript:
+        categorySelectEl = document.getElementById('categories');
+        urlParams = new URLSearchParams(window.location.search);
+        selectedCategory = urlParams.get('category');
+        Array.from(categorySelectEl.children).forEach((option) => {
+          if (option.value == selectedCategory) option.selected = true;
+        });
+        categorySelectEl.addEventListener('change', (e) => {
+          updateParams();
+        })
+- if @contest.offline_form
+  .row
+    .col
+      input type="checkbox" id="offline" style="padding: 5px;"
+      label for="offline"
+        .ms-2
+          = t("contests.scoreboard.hide_offline")
+      javascript:
+        offlineInputEl = document.getElementById('offline');
+        urlParams = new URLSearchParams(window.location.search);
+        offlineInputEl.checked = urlParams.get('hide_offline') == "true";
+        offlineInputEl.addEventListener('change', (e) => {
+          updateParams();
+        })