Start to add architecture documentation [ci skip]

Author: vmadalin

README.md

@@ -105,7 +105,21 @@ Moreover, has been implemented support for [dark theme](https://developer.androi
 
 ## Architecture
 
-//TODO
+The architecture of the application is based, apply and strictly complies with each of the following 5 points:
+
+-   A single-activity architecture, using the [Navigation component](https://developer.android.com/guide/navigation/navigation-getting-started) to manage fragment operations.
+-   [Android architecture components](https://developer.android.com/topic/libraries/architecture/), part of Android Jetpack for give to project a robust design, testable and maintainable. 
+-   Pattern [Model-View-ViewModel](](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel)) (MVVM) facilitating a [separation](https://en.wikipedia.org/wiki/Separation_of_concerns) of development of the graphical user interface.
+-   [S.O.L.I.D](https://en.wikipedia.org/wiki/SOLID) design principles intended to make software designs more understandable, flexible and maintainable.
+-   [Modular app architecture](https://proandroiddev.com/build-a-modular-android-app-architecture-25342d99de82) allows to be developed features in isolation, independently from other features.
+
+### Modules
+
+Modules are collection of source files and build settings that allow you to divide a project into discrete units of functionality. In this case apart from dividing by functionality/responsibility, existing dependence between them:
+
+<p align="center">
+ <img src="screenshots/architecture/modules_diagram.png">
+</p>
 
 ### Build variants
 
@@ -184,6 +198,7 @@ This is project is a sample, to inspire you and should handle most of the common
 -   [android-kotlin-clean-architecture](https://github.com/sanogueralorenzo/Android-Kotlin-Clean-Architecture) (by [sanogueralorenzo](https://github.com/sanogueralorenzo)) - android sample Clean Architecture app written in Kotlin.
 -   [modularization-example](https://github.com/JeroenMols/ModularizationExample) (by [JeroenMols](https://github.com/JeroenMols)) - easy to understand real-life example of a modularized Android app.
 -   [lego-catalog](https://github.com/Eli-Fox/LEGO-Catalog) (by [Eli-Fox](https://github.com/Eli-Fox)) - app illustrating current Android Architecture state using Android development best practices.
+-   [tivi](https://github.com/chrisbanes/tivi) (by [chrisbanes](https://github.com/chrisbanes)) - an app which attempts to use the latest cutting edge libraries and tools.
 -   [android-showcase](https://github.com/igorwojda/android-showcase) (by [igorwojda](https://github.com/igorwojda)) - app following best practices: Kotlin, coroutines, Clean Architecture, feature modules, tests, MVVM, static analysis.
 
 ### Articles