For all Zühlke members: Make Zühlke membership public on your github profile page

[kabaehr]

@Zuehlke/z-heads
For every Zühlke github member it should be visible on his profile, that he is a member of the Zühlke Open Source Community, to give Zühlke more visibility.

Acceptance criterias

• The "Zühlke github badge" is publicly visible on each Zühlke github user's profile
• All members of https://github.com/orgs/Zuehlke/people are set to public

Implementation details:
Everybody has to perform the following steps:

1. Login to github
2. Browse to https://github.com/orgs/Zuehlke/people
3. Search for yourself in the list
4. Select "public" instead of "private" (if not yet)

Test case:

• Logout of your github account
• Browse to your profile
• You should see the Zühlke badge (left side below your profile picture in the "Organizations" section)

Further recommendations:

• Also consider to get yourself listed on the Zühlke Github Page as an active contributor to open source projects or to even list important open source projects there, that you contributed too: Instructions to get listed

[bruderol]

I think we should transfer this into the README file into a "getting started" section for new community members and not keep that as an issue.