feat(client): create an empty language switcher at note level

src/public/app/widgets/note_language.ts

@@ -0,0 +1,30 @@
+import { Dropdown } from "bootstrap";
+import NoteContextAwareWidget from "./note_context_aware_widget.js";
+
+const TPL = `\
+<div class="dropdown note-language-widget">
+    <button type="button" data-bs-toggle="dropdown" aria-haspopup="true" aria-expanded="false" class="btn btn-sm dropdown-toggle select-button note-language-button">
+        <span class="note-language-desc"></span>
+        <span class="caret"></span>
+    </button>
+    <div class="note-language-dropdown dropdown-menu dropdown-menu-left tn-dropdown-list"></div>
+</div>
+`;
+
+export default class NoteLanguageWidget extends NoteContextAwareWidget {
+
+    private dropdown!: Dropdown;
+    private $noteLanguageDropdown!: JQuery<HTMLElement>;
+    private $noteLanguageButton!: JQuery<HTMLElement>;
+    private $noteLanguageDesc!: JQuery<HTMLElement>;
+
+    doRender() {
+        this.$widget = $(TPL);
+        this.dropdown = Dropdown.getOrCreateInstance(this.$widget.find("[data-bs-toggle='dropdown']")[0]);
+
+        this.$noteLanguageDropdown = this.$widget.find(".note-language-dropdown")
+        this.$noteLanguageButton = this.$widget.find(".note-language-button");
+        this.$noteLanguageDesc = this.$widget.find(".note-language-desc");
+    }
+
+}