feat: group board filters in a menu

internal/app/static/board.js

@@ -7,6 +7,20 @@
       return;
     }
 
+    var filterMenu = document.querySelector(".board-filter-menu");
+    if (filterMenu) {
+      document.addEventListener("click", function (event) {
+        if (filterMenu.open && !filterMenu.contains(event.target)) {
+          filterMenu.open = false;
+        }
+      });
+      document.addEventListener("keydown", function (event) {
+        if (event.key === "Escape") {
+          filterMenu.open = false;
+        }
+      });
+    }
+
     var dragged = null;
     var csrf = board.dataset.csrf;