Add example for SharedWorkerGlobalScope

[jfoclpf]

Could you also kindly consider an example with SharedWorkerGlobalScope?

[dipikabh]

Thank you @jfoclpf for your request. We agree that adding an example to demonstrate the use of SharedWorkerGlobalScope would be useful.

We welcome contributions, so if you or anyone else would like to contribute an example, please feel free to submit a pull request. Please note that an addition of an example here will require an update in mdn/content to the relevant page. The update should include a description of the example with a link to this repo for the live demo.