Use mkdocs snippets to template common content blocks (#135)

_snippets/premix-cta.md

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+!!! tip
+        I share (_with my [sponsors](https://github.com/sponsors/funkypenguin)_) a private "_premix_" git repository, which includes necessary docker-compose and env files for all published recipes. This means that sponsors can launch any recipe with just a ```git pull``` and a ```docker stack deploy``` 👍