Add "System Theme" plugin

[jgauth]

I am submitting a new Community Plugin

Repo URL

Link to my plugin: https://github.com/jgauth/obsidian-system-theme

Release Checklist

• [ ] I have tested the plugin on
  • [ ] Windows
  • [ ] macOS
  • [x] Linux
  • [ ] Android (if applicable)
  • [ ] iOS (if applicable)
• [x] My GitHub release contains all required files
  • [x] main.js
  • [x] manifest.json
  • [ ] styles.css (optional)
• [x] GitHub release name matches the exact version number specified in my manifest.json (Note: Use the exact version number, don't include a prefix v)
• [x] The id in my manifest.json matches the id in the community-plugins.json file.
• [x] My README.md describes the plugin's purpose and provides clear usage instructions.
• [x] I have read the tips in https://github.com/obsidianmd/obsidian-releases/blob/master/plugin-review.md and have self-reviewed my plugin to avoid these common pitfalls.
• [x] I have added a license in the LICENSE file.
• [x] My project respects and is compatible with the original license of any code from other plugins that I'm using. I have given proper attribution to these other projects in my README.md.

[jgauth]

additional context for why this plugin exists https://forum.obsidian.md/t/color-scheme-adapt-to-system-not-working-on-linux-fedora-gnome/38743/15

[liamcain]

Oh interesting! I wasn't aware of this bug. We should definitely fix this in the core app. Since the release cycle on our end takes a little while, I think it's fine to have this in the plugin gallery for now. I'll make a note that this is an issue for Linux users and we can take a look at fixing it for good.