Center the buttons in preference section

[Sanya2911]

Fixes #101

Description center the buttons in preference section

Screenshots (if appropriate):

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.

SWOC Participation

• Name: Sanya Saeed
• Discord Username: sanya29#3771
• [X] I have included the issue number in my PR

[Sanya2911]

@developer-diganta is it fine now ?? do I need to add popup.html file also here ??

[Sanya2911]

The changes that I made in popup.html was included in previous issue also, so do I need to include again ??