feat: Added optional dark mode theme properties

[AdrianGonz97]

Linked Issue

Closes #1893

Description

Added optional dark mode specific properties for themes.

These properties can be added via the optional properties_dark prop for custom themes.

Ex:

import type { CustomThemeConfig } from '@skeletonlabs/tw-plugin';

export const customTheme = {
	name: "my-custom-theme",
    // base
    properties: {
        '--color-primary-50': '219 245 236',
        '--color-primary-100': '207 241 230',
        '--color-primary-200': '195 238 224',
		// ...
    },
    // applies on dark theme only (optional)
    properties_dark: {
        '--color-primary-50': '219 245 236',
        '--color-primary-100': '207 241 230',
        '--color-primary-200': '195 238 224',
    }
} satisfies CustomThemeConfig;

Changsets

Instructions: Changesets automate our changelog. If you modify files in /packages/skeleton, run pnpm changeset in the root of the monorepo, follow the prompts, then commit the markdown file. Changes that add features should be minor while chores and bugfixes should be patch. Please prefix the changeset message with feat:, bugfix: or chore:.

Checklist

Please read and apply all contribution requirements.

• This PR targets the dev branch (NEVER master)
• Documentation reflects all relevant changes
• Branch is prefixed with: docs/, feat/, chore/, bugfix/
• Ensure Svelte and Typescript linting is current - run pnpm check
• Ensure Prettier linting is current - run pnpm format
• All test cases are passing - run pnpm test
• Includes a changeset (if relevant; see above)

[changeset-bot]

🦋 Changeset detected

Latest commit: 6ce5efa

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@skeletonlabs/tw-plugin	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated (UTC)
skeleton-docs	✅ Ready (Inspect)	Visit Preview	Aug 17, 2023 8:25pm

[endigo9740]

@AdrianGonz97 looks like a simple enough change that works well enough. Feel free to merge.