Add healthcheck API (For uptimekuma, soon™️)

index.js

@@ -596,6 +596,19 @@ app.get("/api/v1/checkAvailability/:number", (req, res) => {
 	});
 });
 
+app.get("/api/healthcheck", (req, res) => {
+	// Check ability to connect to database with select * from routes
+	db.get('SELECT * FROM routes', [], (err, row) => {
+		if (err) {
+			console.error('Error checking health:', err);
+			res.status(500).send('Internal server error');
+			return;
+		}
+		res.status(200).send('OK');
+	});
+});
+
+
 // Query to get a route
 app.get('/api/v1/route/:apiKey/:ani/:number', (req, res) => {
 	const apiKey = req.params.apiKey;