Fix dark mode on the blog page

**Describe the bug**
Dark mode does not work correctly on the blog page. Only the header's style is turned dark while other elements on the page remain the same.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to the blog section of the website. ([akshitagupta15june.github.io/PetMe/blog.html](https://akshitagupta15june.github.io/PetMe/blog.html))
2. Click on the dark mode button.
3. Scroll down.
4. See that the elements and background remain white rather than turning into a darker color.

**Expected behavior**
Following the styling standards of the website, some elements on the page should turn dark brown when the dark mode button is pressed.

**Screenshots**
When light mode is on:
When dark mode is on:

**Additional context**
I have experience with both React and CSS so I am willing to work on the issue, please assign this to me under SWOC 24.