Create the basic frontend file structure

In the src folder of frontend, we need the following folder structure:

• widgets/ (one folder for each widget, like remote or kinematicunit)
• nav (a folder for the navbar and its components)

Inside of each widget folder, create a react component for that widget. It does not have to contain any logic yet.

Inside of the nav and the src folder, create components as specified in the design statement diagram (e.g. component to add new widget)

This issue is important as it allows all other frontend issues except #19 (closed) , which it depends on like all other frontend issues.