Initial iteration on theming

[adrianthedev]

Context

We need a way to allow the developers to change the appearance of Avo. The initial iteration will cover adding custom CSS variables to a configuration path to get loaded in the front-end.

Initial configuration:

• [ ] primary and secondary colors
• [ ] border-radius (maybe)

Tasks:

• [ ] add configuration for CSS variables (ruby DSL)
• [ ] output the configuration on the front-end
• [ ] customize Tailwind to take them into account
• [ ] change the classes to use that configuration
• [ ] apply the system throughout the app

Second iteration

• [ ] package up that configuration and install it as a gem
• [ ] change the logo with that configuration