Add course material section

[it-vegard]

Explanation

As described in application to Bufdir, we plan to integrate the project in university courses at UiO and OsloMet.
For this to be successful, we need to have tasks and other material readily available at the site.

This should be added as a separate section of the site, linked to from the landing page described in #15.
We should prepare this section for being expanded with new tasks, so that it is possible to learn in steps and perhaps even (further down the line) show progress.

Of course, we need to scope this. As of now, the most urgent need is just having a section with text describing tasks:
What, where and how to do them.

The tasks need to be translated, starting with Norwegian and English.

Suggested solution

Make a new section under each translation, like https://www.clothes4all.net/<en|no>/learning.
Show a list of tasks.
Under this section, add tasks like https://www.clothes4all.net/<en|no>/learning/<task name>.
Link to the learning section from the new landing page.