Add new theme/skins example to starterkit

I was trying to add my own custom theme, and followed the following process:

- Create a new theme based on the starterkit - as per `starterkits/ui_suite_daisyui_starterkit/README.md`
- Run the `npm install` and `npm run build` commands
- Add new theme file in `mytheme/css/themes/fancy.pcss.css` with contents like this:

@plugin "daisyui/theme" {
  name: "fancy";
  default: true;
  prefersdark: false;
  color-scheme: "light";
  --color-base-100: #FAF7F2;
  ...
}

- Add file `mytheme/mytheme.ui_skins.themes.yml` with contents like this:

# No value because same as plugin ID.
fancy:
  label: "Fancy"
  label_context: "color"
  key: "data-theme"
  target: html

- Run the `npm install` and `npm run build` commands again
- Go to `/admin/appearance/settings/mytheme` and select the "Fancy" theme from the "Theme" dropdown

The CSS file for fancy theme is included in the HTML output, and my tag contains `data-theme="fancy".
I can't see any of the colors though...

Is this because I use hex color codes, instead of oklch()?
Or anything else in the process I missed?

It does seem to work if I add it like this in `mytheme/css/themes/fancy.pcss.css`:

:root:has(input.theme-controller[value=fancy]:checked),[data-theme="fancy"] {
  color-scheme: "light";
  --color-base-100: #FAF7F2;
  ...

As per documentation at https://daisyui.com/docs/themes/#how-to-add-a-new-custom-theme, under "If you're using CDN and you want to use a custom theme, use it like this".

I would create a MR to add this to the documentation, but I'm not sure if this is the correct way to implement a custom theme...

@christian.wiedemann can we have a look ?

@svendecabooter

You probably have to edit also the libraries.yml file like this :

core:
  css:
    theme:
      dist/css/app.css: { minified: true }
      dist/css/themes/dark.css: { minified: true }
      dist/css/themes/fancy.css: { minified: true }

Ah yes I did add the CSS like in #9 - forgot to document here.

For me, I had to change the order of the loading of Daisy UI CDN theme. It should be loaded before the custom core library hence I had to add the dependencies to the core library definition in #9

dependencies:
- ui_suite_daisyui/daisyui