[Codebase] Fix the state of Dark mode on pages

[sergiozeppo]

Description

Fixed saving the dark/light theme toggle state on the main pages of the site.

Category

• [ ] Resource Addition
• [ ] Documentation
• [x] Codebase
• [ ] User Interface
• [ ] Feature Addition

Related Issue

Fixes #524

Checklist

• [x] I have followed the CONTRIBUTING guide
• [ ] The name of the resource is spelled correctly (if applicable)
• [ ] The link to the resource is working (if applicable)
• [ ] The resource is added in the correct format (if applicable)
• [x] I have tested changes on my local computer (if applicable)

[netlify[bot]]

✅ Deploy Preview for openpedia ready!

Name	Link
🔨 Latest commit	6f1f7841f82ade1f71c9274d4b24af08c4bbb991
🔍 Latest deploy log	https://app.netlify.com/sites/openpedia/deploys/670a23ab2dceb900087b7661
😎 Deploy Preview	https://deploy-preview-529--openpedia.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.