controlbox: render the toggle via lit-html

src/plugins/controlbox/templates/toggle.html

-<span class="toggle-feedback">{{{o.label_toggle}}}</span>

src/plugins/controlbox/templates/toggle.js

+import { html } from "lit-html";
+import { api } from "@converse/headless/core";
+import { __ } from 'i18n';
+
+export default  () => {
+    const i18n_toggle = api.connection.connected() ? __('Chat Contacts') : __('Toggle chat');
+    return html`<span class="toggle-feedback">${i18n_toggle}</span>`;
+}

src/plugins/controlbox/toggle.js

 import log from "@converse/headless/log";
-import tpl_controlbox_toggle from "./templates/toggle.html";
+import tpl_controlbox_toggle from "./templates/toggle.js";
 import { View } from "@converse/skeletor/src/view";
-import { __ } from '../../i18n';
 import { _converse, api, converse } from "@converse/headless/core";
 import { addControlBox } from './utils.js';
+import { render } from 'lit-html';
 
 const u = converse.env.utils;
 
@@ -31,9 +31,7 @@ const ControlBoxToggle = View.extend({
         // the ControlBox or the Toggle must be shown. This prevents
         // artifacts (i.e. on page load the toggle is shown only to then
         // seconds later be hidden in favor of the controlbox).
-        this.el.innerHTML = tpl_controlbox_toggle({
-            'label_toggle': api.connection.connected() ? __('Chat Contacts') : __('Toggle chat')
-        })
+        render(tpl_controlbox_toggle(), this.el);
         return this;
     },