Add response middleware

Signed-off-by: João Victor Tozatti Risso <jvtr12@inf.ufpr.br>

src/libs/middlewares/response.js

+const xml = require('js2xmlparser');
+
+function response(req, res) {
+    if (req.query.format === 'csv') {
+        res.csv(req.result);
+    } else if (req.query.format === 'xml') {
+        res.send(xml('result', JSON.stringify({ city: req.result })));
+    } else {
+        res.json({ result: req.result });
+    }
+}
+
+module.exports = response;