Adding kanagawa paper theme

[GuelBandeira]

Description

Fixes #830

Type of change

• [ x ] New feature (added a non-breaking change which adds functionality)

How Has This Been Tested?

• [ x ] Tested locally

Checklist:

• [ x ] I have checked to make sure no other pull requests are open for this issue
• [ x ] The code is properly formatted and is consistent with the existing code style
• [ x ] My changes generate no new warnings

Screenshots

[Copilot]

Pull request overview

This PR adds the "kanagawa-paper" theme to the theme collection and implements alphabetical sorting of themes in the demo page. The PR also includes an "oceanic-next" theme addition, though this was not mentioned in the title.

• Added "kanagawa-paper" theme with appropriate color scheme
• Added "oceanic-next" theme with appropriate color scheme
• Implemented alphabetical sorting of themes in the demo dropdown
• Applied code formatting improvements (foreach syntax consistency, whitespace cleanup)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/themes.php	Adds two new theme definitions: "oceanic-next" and "kanagawa-paper" with color configurations
src/demo/index.php	Implements alphabetical theme sorting via ksort() and applies code formatting improvements to foreach statements and whitespace

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[DenverCoder1]

Thanks for contributing!