add README file

README.md

+# MAdLand - Molecular Adaptation to Land: plant evolution to change
+
+This ARC was created as part of the [MAdLand project](https://madland.science/)
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+
+## Project metadata
+
+Most metadata can be found in the `studies/` folder, the `isa.study.xlsx` file contains multiple sheets with metadata, including:
+
+- Sample Sheet
+- Harvesting metadata
+- Culturing Conditions
+
+Information about the assays (e.g. RNASeq) can be found in the the respective `assays/` folder.
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+