Support Light/Dark Themes for the Blog by user's preferred theme

**Description**
- As a user of our blog, I want the blog to automatically switch to a light or dark theme based on my preferred theme setting.

**Acceptance Criteria**
- The blog should automatically switch to the user's preferred theme based on their browser or device settings
- If the user does not have a preferred theme setting, the default theme should be used
- The user should be able to manually switch between light and dark themes using a toggle switch