add new market data for osnabrueck

[BjoernSchilberg]

I added the markets from Osnabrück.

[johnjohndoe]

I appreciate your contribution. Please note that we support German Umlauts as mentioned in the contribution guide. Please rename osnabrueck.json to osnabrück.json and adapt the change in cities.json as follows:

"osnabrück": {
    "id": "osnabrück",
    "label": "Osnabrück"
},

You are welcome to update this pull request. You can update your commit using git commit --amend and then update the branch on GitHub via git push --force market-data-osnabrueck. Let me know if you need help in any case.

[BjoernSchilberg]

Done. Thanks for the hint.

[johnjohndoe]

@BjoernSchilberg I appreciate the nice and clean pull request and I like to welcome you on Wo ist Markt? 💐

In order to promote the project I would like to ask you for two follow up tasks:

• Send a tweet #woistmarkt with a screenshot and a link to the website (please share the tweet link here)
• Try to convince the city of Osnabrück to link to our website, see Promote website #38

You are also very welcome to improve the code. Please take a look at our issue tracker.