chore: install cssbundling rails and set up compilation

spec/dummy/node_modules/@sindresorhus/merge-streams/index.d.ts

@@ -0,0 +1,21 @@
+/**
+Merges an array of [readable streams](https://nodejs.org/api/stream.html#readable-streams) and returns a new readable stream that emits data from the individual streams as it arrives.
+
+If you provide an empty array, it returns an already-ended stream.
+
+@example
+```
+import mergeStreams from '@sindresorhus/merge-streams';
+
+const stream = mergeStreams([streamA, streamB]);
+
+for await (const chunk of stream) {
+	console.log(chunk);
+	//=> 'A1'
+	//=> 'B1'
+	//=> 'A2'
+	//=> 'B2'
+}
+```
+*/
+export default function mergeStreams(streams: NodeJS.ReadableStream[]): NodeJS.ReadableStream;