Add Picrust2 install procedure on tars

picrust2/README.md

+# PICRUSt2
+
+[PICRUSt2](https://github.com/sunbeam-labs/sunbeam) is a software for predicting functional abundances based only
+on marker gene sequences.
+
+Here is a brief note to help you use PICRUSt2 at Pasteur on TARS. You can also read the
+full [documentation](https://github.com/picrust/picrust2/wiki) or get more information from the 
+[preprint](https://www.biorxiv.org/content/10.1101/672295v1).
+
+## Install
+
+### Prerequisite
+
+[Conda](https://docs.conda.io/projects/conda/en/latest/user-guide/install/index.html) is required for the
+basic install of the tool. We might set up a singularity image in the future.
+
+### Procedure
+
+Please refer to the [documentation](https://github.com/picrust/picrust2/wiki/Installation) to get the latest
+procedure. You can [install from bioconda](https://github.com/picrust/picrust2/wiki/Installation#install-from-bioconda)
+of [install from source](https://github.com/picrust/picrust2/wiki/Installation#install-from-source).
+
+> **Warning** You need internet access to do that so you need to perform install on
+the head of submission.
+
+## Run PICRUSt2
+
+You can follow the [documentation](https://github.com/picrust/picrust2/wiki/Full-pipeline-script)
+to run the full picrust2 workflow.