[Branding] Allow the modifcation of the theme colors

[bautisflow]

Is your feature request related to a problem? Please describe.
I can't set the color scheme for the main color of the menu and buttons. More specifically colors #132533 and #1F8EFE. Being allowed to set this colors would make a better fit with the company or client colors in the rebranding.

Describe the solution you'd like
In Brand Details, rename the 'Top Bar' tab to 'Theme' and add, apart from setting the top bar background and text colors, the primary and secondary colors.

Describe alternatives you've considered
The alternative is to remain with Thinger.io brand colors.