Node.js: response body chunk can now be a Uint8Array.

Starting from Node.js 15.0.0 the chunk parameter of the response.write()
can be a Uint8Array.

This closes #870 issue on GitHub.

test/node/write_array/app.js

@@ -0,0 +1,4 @@
+require('http').createServer(function (req, res) {
+    res.writeHead(200, {'Content-Length': 5, 'Content-Type': 'text/plain'})
+        .end(new Uint8Array(Buffer.from('array', 'utf8')));
+}).listen(7080);