Add file structure section to client overview

docs/source/overview/client.md

 # Client overview
+
+The client is the main part of the system.
+It is divided into 4 parts: login, admin, presentation editor and active competitions (presentations).
+The presentations is also further divided into four different parts: operator view, audience view, team view and judge view.
+
+## File structure
+
+All of the actual pages in the system is stored in the `client/src/pages/` folder.
+For each of the different parts there is a corresponding file that ends in Page, for example `JudgeViewPage.tsx` or `LoginPage.tsx`.
+This is the main file for that page.
+All of these pages also has their own and shared components, in the folder relative to the page `./components/`.