refactor: implement a new design for the UI

[uAtomicBoolean]

Improvements to the UI:

• Remove icons from the header links and add an underline like tab navigation.
• Set background color of main page to a grayish color.
• Rework the script's card to have a new button Execute with the card still being clickable.
• Rework the about and settings page to fit the new design.
• Rework the add script modal and the script's settings modal.

Add script modal and script's settings:

• Both modal would be merged in a single modal with a field to toggle or not the delete button.
• the following settings would be displayed by default: name, interpreter, file selector, arguments.
• The following settings would hidden in another tab or in a collapse: administrator, notification.