What does this PR do?
Removed the horizontal scrollbar of topics from the UI for medium to large devices.

Related Issue(s)
Closes #52

Changes
Updated the overflow-x property of selectionMenu to hidden for large devices and makes it scroll for small devices for better UI. Also centers the selectionMenu topics.

Screenshots or GIFs (if applicable)

Checklist

• I have read and followed the contributing guidelines.
• My code follows the project's coding style and conventions.
• I have added unit tests (if applicable) to ensure the code works as expected.
• I have updated the project documentation (if necessary).

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