Add dummy topic dropdown in layout.html

[ByteOtter]

What does this PR change?

Added a dropdown menu with some pre defined topics. Moved About page link to profile dropdown temporarily.

Tick the applicable box:

• [ ] Add new feature

• [x] UI improvement

• [ ] Changed routing

• [ ] Security changes

• [ ] Testsuite
  

• [ ] General Maintenance

UI changes

provide description here or remove all unapplicable lines below

before: About link visible directly in the navbar on the left side.

after: About link replaced by a topic dropdown.

• [x] DONE

Links

In case your changes fix an existing issue please link it below:

Tracks: #92

• [x] DONE

Documentation

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• No documentation needed
  

• [x] DONE