Add Mikrotik WinBox container for GNS3

[alexhorner]

Add Mikrotik WinBox container for GNS3 based on https://github.com/alexhorner/winbox-dockerised

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When creating a new appliance:

• It's tested locally, i.e.
  • [X] You dragged an instance into a project on your box, got it installed (if necessary), and did some basic network checks (ping, UI reachable, etc.).
  • [X] GNS3 VM can run it without any tweaks.
  • [X] The device is in the right category: router, switch, guest (hosts), firewall
  • [X] You filled in as much info as possible (checks the schemas and other appliance files for some guidance).
• [X] When adding a container: it builds on Docker Hub and can be pulled.
• [ ] The filenames in the "images" section are unique (to avoid appliances and/or versions overwriting each other).
• [x] If you forked the repo, running check.py doesn't drop any errors for the new file.
• [ ] Optional: a symbol has been created for the new appliance.

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Images section has been left unticked as I did not include an images section, based on referencing other container JSON files

[grossmj]

Thanks for your contribution! :)