ENH: Update README.md

Author: RafaelPalomar

README.md

@@ -1 +1,11 @@
 # ALiveResearchTestingData
+
+This is a mirror for storing ALive-research testing data assets and it is based on [SlicerTestingData](https://github.com/Slicer/SlicerTestingData).
+
+To support content-based addressing, files are uploaded as assets organized in [releases](https://github.com/ALive-Research/ALiveResearchTestingData/releases)
+named after the hashing algorithm.
+
+For each hashing algorithm `<HASHALGO>` (MD5, SHA256, ...), you will find:
+* release named `<HASHALGO>`
+* a CSV file `<HASHALGO>.csv` listing all `<hashsum>;<filename>` pairs
+* markdown document `<HASHALGO>.md` with links of the form `* [<filename>](https://github.com/ALive-Research/ALiveResearchTestingData/releases/download/<HASHALGO>/<checksum>)` (this file is regenerated on each upload from the CSV file, therefore files should be renamed or deleted by editing the CSV file)