Add Bootstrap 5.2 support

[FelipoAntonoff]

Hello, I would like to suggest an upgrade from Bootstrap 3 to 5.2, as it is already very stable and has new features, in addition to not using Jquery anymore, but JS vanilla.

I believe that with Bootstrap 5, the theme will be more current and easier to customize.

Version 5 was released 05/05/2021 and has already had several sub versions with improvements, 5.2 being the most current released 18 days ago, page about it: https://getbootstrap.com/docs/5.2/getting-started/ introduction/