docs(shortcodes): Add example repository badge

[niclasheinz]

Hi @squidfunk

There are some example repositories at https://github.com/mkdocs-material, but these are not listed in the documents. With the new badge, the example repositories can be linked in the documentation.

[squidfunk]

Thanks for the PR. Just to knit pick, I'm not really happy with "examplerepo". Also, where would we use it? Could you add suggestions in this PR, so we can learn whether we really want/need this?

[niclasheinz]

I've updated the PR. I thought it would be useful if the existing template repositories from github.com/mkdocs-material were linked in the documentation.

[kamilkrzyskow]

I think it's a good addition to the example, which links to downloadable zip archives.

Likewise to squidfunk I think that the name examplerepo together with Example repository could be improved 🤔.
How about demo and Demonstration, as the repositories could have their own rendered pages?

[niclasheinz]

How about demo and Demonstration, as the repositories could have their own rendered pages?

Good point. That's definitely a better formulation than the one I made.

[squidfunk]

+1 for Kamil's proposal!