Migrate gulp logic to ESM equivalent

CI has been failing ever since the migration of the code to use ESModules - we should consider migrating to a different tooling for what is currently just parsing Markdown files to their HTML equivalent

Perhaps we could also consider using [Analog](https://analogjs.org/) which offers the ability to [render content using a pre-processor](https://analogjs.org/docs/features/routing/content) (this would remove the need to still fetch the HTML content to be inserted into the DOM)