fix(deps): update dependency reveal.js to v5.2.1

Author: renovate[bot]

package.json

@@ -15,7 +15,7 @@
   "dependencies": {
     "@vuepress/bundler-vite": "2.0.0-rc.9",
     "@waline/client": "3.3.2",
-    "reveal.js": "5.1.0",
+    "reveal.js": "5.2.1",
     "vue": "3.5.12",
     "vuepress": "2.0.0-rc.9",
     "vuepress-theme-hope": "2.0.0-rc.40"