Relocate toml lint task to buildSrc and extend against default task

Fixes build errors after Gradle 9.x upgrade

Ref: https://docs.gradle.org/current/userguide/implementing_custom_tasks.html

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

buildSrc/build.gradle.kts

@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2025 NewPipe e.V. <https://newpipe-ev.de>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+plugins {
+    `kotlin-dsl`
+}
+
+repositories {
+    gradlePluginPortal()
+}