chore: add yarn command to put compiled stylesheets into builds folder

node_modules/@sindresorhus/merge-streams/index.js

@@ -0,0 +1,39 @@
+import {PassThrough as PassThroughStream} from 'node:stream';
+
+export default function mergeStreams(streams) {
+	if (!Array.isArray(streams)) {
+		throw new TypeError(`Expected an array, got \`${typeof streams}\`.`);
+	}
+
+	const passThroughStream = new PassThroughStream({objectMode: true});
+	passThroughStream.setMaxListeners(Number.POSITIVE_INFINITY);
+
+	if (streams.length === 0) {
+		passThroughStream.end();
+		return passThroughStream;
+	}
+
+	let activeStreams = streams.length;
+
+	for (const stream of streams) {
+		if (!(typeof stream?.pipe === 'function')) {
+			throw new TypeError(`Expected a stream, got: \`${typeof stream}\`.`);
+		}
+
+		stream.pipe(passThroughStream, {end: false});
+
+		stream.on('end', () => {
+			activeStreams--;
+
+			if (activeStreams === 0) {
+				passThroughStream.end();
+			}
+		});
+
+		stream.on('error', error => {
+			passThroughStream.emit('error', error);
+		});
+	}
+
+	return passThroughStream;
+}