webapp: declare emitted event in FormFooter component

fixes an annoying warning (visible in the browser console):

[Vue warn]: Extraneous non-emits event listeners (reload) were passed to
component but could not be automatically inherited because component
renders fragment or text root nodes. If the listener is intended to be a
component custom event listener only, declare it using the "emits"
option.

webapp/src/components/FormFooter.vue

@@ -7,3 +7,9 @@
         <button type="submit" class="btn btn-primary">{{ $t('base.Save') }}</button>
     </div>
 </template>
+
+<script lang="ts">
+export default {
+    emits: ['reload'],
+};
+</script>