feat: add button to clear active filters (#924)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/924
Reviewed-by: dpschen <dpschen@noreply.kolaente.de>
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>

src/i18n/lang/en.json

@@ -344,6 +344,7 @@
   },
   "filters": {
     "title": "Filters",
+    "clear": "Clear Filters",
     "attributes": {
       "title": "Title",
       "titlePlaceholder": "The saved filter title goes here…",