return 200 and piston ver on /, fix empty content-type header validation

api/package.json

@@ -1,6 +1,6 @@
 {
     "name": "piston-api",
-    "version": "3.1.0",
+    "version": "3.1.1",
     "description": "API for piston - a high performance code execution engine",
     "main": "src/index.js",
     "dependencies": {

api/src/api/v2.js

@@ -163,7 +163,7 @@ router.use((req, res, next) => {
         return next();
     }
 
-    if (!req.headers['content-type'].startsWith('application/json')) {
+    if (!req.headers['content-type']?.startsWith('application/json')) {
         return res.status(415).send({
             message: 'requests must be of type application/json',
         });

api/src/index.js

@@ -79,6 +79,12 @@ expressWs(app);
     const api_v2 = require('./api/v2');
     app.use('/api/v2', api_v2);
 
+    const { version } = require('../package.json');
+
+    app.get('/', (req, res, next) => {
+        return res.status(200).send({ message: `Piston v${version}` });
+    });
+
     app.use((req, res, next) => {
         return res.status(404).send({ message: 'Not Found' });
     });