Update readme to reflect JS library download no longer required

Thanks for this, there are a couple of complications we'll need to sort out first.

If we commit this patch as-is it will revert any sites that have gone to the effort of installing the library to using the CDN which isn't necessarily going to break them, but could cause some outages.

I agree that installing with composer is ideal - can you provide the method with which you achieved that? Perhaps we can roll that into the module.

If we can automate the library inclusion in a standardised and future-proofed way, it's probably worth a minor release with a big fat warning on it and remediation instructions as there are already over 1k sites reporting usage of 4.1.x.

While adding GitLab CI I switched the builder from gulp to vite, it would be very easy to bundle the library directly into this package and I'm tempted to do so.

@anand.tshniwal93 I've come back to review this and I have to ask - how are you using composer to install an npm dependency? That is not something supported by composer.

I'm going to mark this postponed for a minimum of 1 month for further feedback, and potentially close as "works as designed" after that.

I'd encourage anyone having issues with JS dependencies to check out a work-in-progress solution to this problem at https://github.com/darvanen/drupal-js

As of 4.2.0 the slide-element library is now bundled into the built code. It is no longer necessary to mess around with CDNs or downloaded libraries. I'm updating the readme to reflect this.