Move check all js into separate file

bookwyrm/static/js/check_all.js

@@ -0,0 +1,24 @@
+// Toggle all checkboxes.
+window.onload = function() {
+    document
+        .querySelectorAll('[data-action="toggle-all"]')
+        .forEach(input => {
+            input.addEventListener('change', toggleAllCheckboxes);
+        });
+};
+
+/**
+ * Toggle all descendant checkboxes of a target.
+ *
+ * Use `data-target="ID_OF_TARGET"` on the node being listened to.
+ *
+ * @param  {Event} event - change Event
+ * @return {undefined}
+ */
+function toggleAllCheckboxes(event) {
+    const mainCheckbox = event.target;
+
+    document
+        .querySelectorAll(`#${mainCheckbox.dataset.target} [type="checkbox"]`)
+        .forEach(checkbox => {checkbox.checked = mainCheckbox.checked;});
+}