[FEATURE] Theming support

[laaledesiempre]

Adding theming support.

something like that on the start page.

[laaledesiempre]

Planning on theme support:

• Creating a class that manages theming.
• Adding Trollian theme.
• Implement on theme's class a Factory design pattern.
• Developing a modal screen to create new color themes.
• Saving custom theme as localStorage or cookie.

Testing as beta feature

Adding background support (#16)

This is to get some feedback about how to improove it.

• Implement feedback.
• Multiple custom theme support
• Opacity support

Testing as beta feature

• Add a custom way to share themes as strings.
• Exporting themes as txt or specific extension to load them in the future.

i want to make this an specially good feature, i think that is also a great way to show the quality of our thing :33