Implement lessons list screen

[The Figma document](https://www.figma.com/file/uLiqrlxmOB5xCppIzmiUXV/Teacher-Workout?node-id=0%3A1) contains the entire UI of the project.

You can export any image (asset) directly from Figma. [Here's how](https://drive.google.com/file/d/1KJncuAGFvKEo6zrjC9H3O59auITE0q2h/view).

**Please do not try to recreate the UI design exactly.** Prioritize using de default UI mobile components, and following the material design guidelines. The UI objects should be positioned roughly the same as in the Figma screens.

[The mobile flow can be found in the project Wiki](https://github.com/code4romania/teacher-workout-backend/wiki/Teacher-Workout-Mobile-flow).

_Please define related colors and text & button styles in the corresponding values files. Please extract all text values in the corresponding xml files so we can easily adjust them. <3_

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Pressing the back button will take the user back in the [lesson themes listing screen](https://drive.google.com/file/d/1PGH4w2ilLl8RpuEG6wmdWkcOONiKOEiW/view?usp=sharing). The same will happen when the user presses the X (close) button.

The lesson list will scroll down to reveal all the lessons within this category.

Each lesson title, category title, estimated reading time will be pulled from the corresponding backend endpoint. _(We will link the staging env for the backend and list the endpoint as soon as we define them)_

Each lesson progress will be pulled from the current user's stored progress.