docs: depreciation notice

README.md

 # mir-prepare-annotation
 
+**NOTE: THIS IS AN OUTDATED VERSION OF THE ZAVOLAB MIRNA PIPELINE SUITE, IN
+WHICH EACH PIPELINE LIVES INSIDE ITS OWN REPOSITORY. GIVEN THAT THE PIPELINES
+ARE USUALLY RUN TOGETHER AND THEY SHARE A LOT OF THE SAME RESOURCES, WE HAVE
+SINCE DECIDED TO HOST ALL PIPELINES IN THE SAME (THIS!) REPOSITORY, UNDER THE
+DEFAULT BRANCH. YOU ARE STRONGLY RECOMMENDED TO USE THE NEW SETUP, AS THIS
+BRANCH AND THE OTHER REPOSITORIES ARE NOT MAINTAINED ANYMORE.**
+
 [Snakemake][snakemake] workflow to download and prepare the necessary files for
 smallRNA-seq related pipelines [mir-map][mir-map] and [mir-quant][mir-quant].