fix(backend): バックエンドのpnpm devによるビルド後にbuild-assetsを行うようにする (#13659)

* moveto scripts

* add scripts/dev.mjs

packages/backend/scripts/watch.mjs

@@ -0,0 +1,28 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { execa } from 'execa';
+
+(async () => {
+	// なぜかchokidarが動かない影響で、watchされない
+	/*
+	execa('tsc-alias', ['-w', '-p', 'tsconfig.json'], {
+		stdout: process.stdout,
+		stderr: process.stderr,
+	});
+	*/
+
+	setInterval(() => {
+		execa('tsc-alias', ['-p', 'tsconfig.json'], {
+			stdout: process.stdout,
+			stderr: process.stderr,
+		});
+	}, 3000);
+
+	execa('tsc', ['-w', '-p', 'tsconfig.json'], {
+		stdout: process.stdout,
+		stderr: process.stderr,
+	});
+})();