fix(#10): Add Docker HEALTHCHECK on /health endpoint and document healthy/unhealthy criteria

docs/healthcheck.md

@@ -0,0 +1,35 @@
+# Healthcheck
+
+## Endpoint
+
+The application exposes a `/health` endpoint at the root level which returns a JSON response indicating the health status of the application.
+
+### Example Response
+
+```json
+{
+  "status": "ok"
+}
+```
+
+## Docker HEALTHCHECK
+
+The Docker image includes a `HEALTHCHECK` instruction that verifies the application's health by making an HTTP request to the `/health` endpoint.
+
+### Healthcheck Configuration
+
+- **Interval**: 30 seconds
+- **Timeout**: 10 seconds
+- **Start Period**: 5 seconds
+- **Retries**: 3 attempts
+
+### Healthy Status
+
+The container is considered healthy if the `/health` endpoint returns a successful HTTP response (status code 2xx).
+
+### Unhealthy Status
+
+The container is considered unhealthy if:
+
+1. The `/health` endpoint is unreachable.
+2. The `/health` endpoint returns an error status code (4xx or 5xx).