add index endpoint

app.js

@@ -14,6 +14,10 @@ const IROHA_ASSET = process.env.IROHA_ASSET || "coin";
 const DATA_OWNER = process.env.DATA_OWNER || "admin"
 const PRICE_MODIFIER = process.env.PRICE_MODIFIER || 0.5;
 
+app.get("/", (req, res) => {
+    res.send("Chain4All Blockchain service");
+});
+
 app.post("/price", (req, res) => {
     if (req.body && req.body.extent) {
         res.send({ price: getPrice(req.body.extent) });