CSS: Fix horizontally centered spinner

sass/_core.scss

@@ -498,6 +498,7 @@ body.converse-fullscreen {
         margin: auto;
     }
     .hor_centered {
+        width: 100%;
         text-align: center;
         display: block;
         margin: 0 auto;

src/templates/login_panel.js

@@ -76,6 +76,6 @@ export default (o) => html`
             <p class="feedback-subject">${ o.conn_feedback_subject }</p>
             <p class="feedback-message ${ !o.conn_feedback_message ? 'hidden' : '' }">${o.conn_feedback_message}</p>
         </div>
-        ${ (o._converse.CONNECTION_STATUS[o.connection_status] === 'CONNECTING') ? tpl_spinner() : form_fields(o) }
+        ${ (o._converse.CONNECTION_STATUS[o.connection_status] === 'CONNECTING') ? tpl_spinner({'classes': 'hor_centered'}) : form_fields(o) }
     </form>
 `;

src/templates/spinner.js

 import { html } from "lit-html";
 
-export default () => html`<span class="spinner fa fa-spinner centered"/>`
+export default (o) => html`<span class="spinner fa fa-spinner centered ${o.classes || ''}"/>`