feat: support dark theme for utterances and giscus

data/siteMetadata.js

@@ -32,6 +32,8 @@ const siteMetadata = {
       // theme example: light, dark, dark_dimmed, dark_high_contrast
       // transparent_dark, preferred_color_scheme, custom
       theme: '',
+      // theme when dark mode
+      darkTheme: '',
       // If the theme option above is set to 'custom`
       // please provide a link below to your custom theme css file.
       // example: https://giscus.app/themes/custom_example.css
@@ -44,6 +46,8 @@ const siteMetadata = {
       // theme example: github-light, github-dark, preferred-color-scheme
       // github-dark-orange, icy-dark, dark-blue, photon-dark, boxy-light
       theme: '',
+      // theme when dark mode
+      darkTheme: '',
     },
     disqus: {
       // https://help.disqus.com/en/articles/1717111-what-s-a-shortname