Add deprecation notice

README.md

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+**This is the outdated version 2 of FacilMap. Find the newest version of FacilMap on the [master branch](https://github.com/FacilMap/facilmap) or in the [facilmap/facilmap](https://hub.docker.com/r/facilmap/facilmap) Docker image.**
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 [**FacilMap**](https://facilmap.org/) is an online map that aims to bring together many useful functions in a usable and pretty way onto an
 open-source map based on [OpenStreetMap](https://openstreetmap.org/). Features include: