added readme

README.md

+# What is this tool?
+
+Let's all be frank, root sucks and the root file format is horrible.
+It's among humanities worst pieces of software. With this small tool I hope to fix
+the damage that was done, at least a little, by converting root files into
+native Python formats.
+
+
+It's using [Numpy](https://numpy.org) and a library called [Uproot](https://github.com/scikit-hep/uproot5)
+to read and process these damn root files. So far it is specialist for one task
+and I will have to work on it to make it actually viable for more use cases. That task
+is to extract PXD data from Belle 2 data files.
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