Add notice - obsolete doc

README.md

 # Metacentrum Cloud Documentation
 
+
+**Note that this documentation is getting obsolete, use [e-infra_cz doc repo](https://gitlab.ics.muni.cz/einfra-docs/documentation) instead.**
+
 ## Run development server
 
 ```
 hugo serve --config config-dev.toml --bind 127.0.0.1 --port 1313
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+```