feat: add dark mode support

Enable dark mode toggling for the theme:
- Change colorSchema from "light" to "both" in package.json
- Import dark-mode.css with color scheme overrides for all 50+ schemes
- Add dark mode styling for inline code elements
- Update example.md to use colorSchema: auto

Note: Dark mode colors could use some refinement for better aesthetics.

Closes #1

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gureckis

example.md

@@ -1,5 +1,5 @@
 ---
-colorSchema: light
+colorSchema: auto
 layout: cover
 routerMode: hash
 title: Base Template

package.json

@@ -44,7 +44,7 @@
   },
   "homepage": "https://gureckis.github.io/slidev-theme-neversink/",
   "slidev": {
-    "colorSchema": "light",
+    "colorSchema": "both",
     "highlighter": "all"
   },
   "devDependencies": {

styles/base.css

@@ -159,6 +159,12 @@ html.dark {
   .slidev-layout {
     color: #d0d0d0;
   }
+
+  /* inline code blocks in dark mode */
+  .slidev-layout :not(pre) > code {
+    background: #334155; /* slate-700 */
+    color: #e2e8f0; /* slate-200 */
+  }
 }
 
 html:not(.dark) {