add new Markdown assessment for READMEs

[avallecam]

Use a combination of behavioural and constructivist theory:

• watch a motivational live demo on 'what I write is not what I see' with markdown
• read a how-to guide on markdown for reporting issues or writing readmes on github
• discuss in groups on the good practices and features applied to selected readme files
• write an issue and a readme
  1. identify an existing readme that you read in the past and would like to improve (from you, your team, or a colleague)
  2. create an issue
  3. edit the file following your edit suggestions (then this will suggest you to fork, create a branch, make a pull request)
  4. share the pull request link in our discussion entry