Clean up ServiceWorker examples

[lidel]

I started deprecating ancient ServiceWorker demos we have all over the place and pointing people at the modern example created by @Gozala at ipfs/js-ipfs/examples/browser-service-worker

This issue tracks the cleanup process:

• docs(readme): deprecation notice ipfs-inactive/ipfs-service-worker-demos#20
• deps(dev): bump webpack-dev-server from 4.15.1 to 5.0.2 service-worker-gateway#45

Each of the above should be merged → repo archived → moved to @ipfs-inactive