Remove Tailwind CSS UI and updated deps.

[wildpow]

Remove Tailwind UI

• I believe this is a pay-for project which would be of no use for most people using this starter.

Update Dependencies

• Minor version bump to Svelte.
• Minor version bump to PostCSS.
• Major update to Rollup from v1 to v2.

---

NOTE

• @rollup/plugin-commonjs was not updated due to issue 1151.

[wildpow]

Tested dev, prod and export scripts. The only difference I saw was the console warning

> To preserve the export signature of the entry module "src/client.js", an empty
 facade chunk was created. This often happens when creating a bundle for a 
web app where chunks are placed in script tags and exports are ignored. 
In this case it is recommended to set "preserveEntrySignatures: false"
 to avoid this and reduce the number of chunks. Otherwise if this is intentional,
 set "preserveEntrySignatures: 'strict'" explicitly to silence this warning.

I found a merged Rollup PR 3498 but, nothing else to indicate this being a show stopper.

[babichjacob]

The Tailwind UI plugin provides colors and other extensions to Tailwind CSS that will make their way into a future update (i.e. are free for everyone).

This is different from the (paid) Tailwind UI package of HTML components, which is dependent on the Tailwind UI plugin (or using the CDN build of it).

Because the plugin is currently commented out in tailwind.config.js because I haven't figured out why there is a recursion error using it during development (but not production), I will approve these changes anyway.

[babichjacob]

Tested dev, prod and export scripts. The only difference I saw was the console warning

> To preserve the export signature of the entry module "src/client.js", an empty
 facade chunk was created. This often happens when creating a bundle for a 
web app where chunks are placed in script tags and exports are ignored. 
In this case it is recommended to set "preserveEntrySignatures: false"
 to avoid this and reduce the number of chunks. Otherwise if this is intentional,
 set "preserveEntrySignatures: 'strict'" explicitly to silence this warning.

I found a merged Rollup PR 3498 but, nothing else to indicate this being a show stopper.

Right, it's fine. The other template has moved to Rollup v2 with no trouble. Maybe it'll be possible to silence this warning in onwarn in rollup.config.js.