Add a new scenario to test basic Wiki functionalities

This will automatize the Wiki operations part of https://docs.google.com/spreadsheets/d/15AtBb6s2p_HvtUe5G9GUSc2ngt69X8dO-418zMuT4us/edit?ts=5b07999b#gid=0.

1. Create a project
2. Access its wiki
3. Create a page
4. Access the newly created page => assert that the page is created and contains the expected content
5. Modify the page => assert that the change is visible

Further improvements / Second iteration:

1. Clone the wiki
2. Modify the page locally
3. Push the change
4. Visit the wiki page => assert that the change is visible