Add smoke test

[szkiba]

A smoke.test.js file should be created that contains a simple smoke test of the extension and can be successfully run without any external dependencies with a k6 that includes the extension.

Background

The k6lint and k6-extension-registry smoke checker checks the existence and successful execution of the smoke test after build.

If there is no smoke test, the extension gets a lower grade. In this case:

In the simplest case, the smoke test only contains the import of the extension and an empty default function.

See also:

• https://github.com/grafana/k6lint#checkers
• https://github.com/grafana/k6-extension-registry/wiki/Compliance
• https://github.com/grafana/k6-extension-registry/wiki/OKRs
• https://github.com/grafana/xk6-faker/blob/master/smoke.test.js
• https://github.com/grafana/xk6-sql/blob/main/smoke.test.js