fix: widen padding at sidebar top

[SoCuul]

What kind of change does this PR introduce?

check at least one

• [x] Bugfix
• [ ] Feature
• [ ] Refactor
• [ ] Other, please describe:

Validations

• [x] Follow our CONTRIBUTING guide

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I can't speak for other platforms, but on macOS the default placement of the sidebar is much too close to the window buttons for comfort. I've accidentally minimized/maximized my massCode window by misclicking because of the narrow space in between the "Library / Tags" button and the window controls.

This pull request increases the padding to better separate the in-app controls from the system window controls. Eg. after: