class-strategy dark mode compatible giscus theme

<Giscus
    // ...
    theme="https://my-trash-bin.github.io/giscus-theme/github.css"
    // ...
/>

Available themes

• https://my-trash-bin.github.io/giscus-theme/github.css
• https://my-trash-bin.github.io/giscus-theme/github_high_contrast.css
• https://my-trash-bin.github.io/giscus-theme/github_protanopia.css
• https://my-trash-bin.github.io/giscus-theme/github_tritanopia.css

You don't need this

See giscus/giscus-component#2076.