[cr146] Fixing CrLitElement tslint warnings

Chromium changes:
https://chromium.googlesource.com/chromium/src/+/079a94e886ed77cdd2eda001a2bc289bc945aedb

commit 079a94e886ed77cdd2eda001a2bc289bc945aedb
Author: dpapad <dpapad@chromium.org>
Date:   Wed Feb 4 12:39:25 2026 -0800

    WebUI: Implement new @webui-eslint/lit-element-structure check.

    Specifically the new check enfocres the following for CrLitElement
    subclasses:
     1) The exstence of the 'static get is() {...}' method.
     2) The existence of the 'interface HTMLElementTagNameMap {...}'
        declaration.
     3) The existence of the 'customElements.define(...)' call.

    All violations have been addressed in previous CLs and the check is
    enabled as part of build_webui's ':lint_ts' target.

    Some additional structural checks will be added in follow-up CLs.

    Bug: 480028273
    Change-Id: I2683d9bd72598a1448efdc6224da5c5b70c3e4a0
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7536164
    Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
    Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1579659}

browser/resources/brave_education/brave_education_app.ts

@@ -144,4 +144,10 @@ export class BraveEducationAppElement extends CrLitElement {
   }
 }
 
+declare global {
+  interface HTMLElementTagNameMap {
+    'brave-education-app': BraveEducationAppElement
+  }
+}
+
 customElements.define(BraveEducationAppElement.is, BraveEducationAppElement)