fix(frontend): フォーカス/タブ移動に関する挙動を調整 (#226)

Cherry-pick commit e8c030673326871edf3623cf2b8675d68f9e1b13

Co-authored-by: taiyme <53635909+taiyme@users.noreply.github.com>

packages/frontend/src/scripts/focus.ts

@@ -1,32 +0,0 @@
-/*
- * SPDX-FileCopyrightText: syuilo and misskey-project
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-export function focusPrev(el: Element | null, self = false, scroll = true) {
-	if (el == null) return;
-	if (!self) el = el.previousElementSibling;
-	if (el) {
-		if (el.hasAttribute('tabindex')) {
-			(el as HTMLElement).focus({
-				preventScroll: !scroll,
-			});
-		} else {
-			focusPrev(el.previousElementSibling, true);
-		}
-	}
-}
-
-export function focusNext(el: Element | null, self = false, scroll = true) {
-	if (el == null) return;
-	if (!self) el = el.nextElementSibling;
-	if (el) {
-		if (el.hasAttribute('tabindex')) {
-			(el as HTMLElement).focus({
-				preventScroll: !scroll,
-			});
-		} else {
-			focusPrev(el.nextElementSibling, true);
-		}
-	}
-}