add README with overview urls

README.md

+# Efficient Distributed GPU Programming for Exascale
+
+_A proposal for a SC21 tutorial_
+
+## Sample Material
+
+Since the tutorial is a combination of and extension upon previous material, we fail to select one singular URL to provide samples and visual aid. Please rather refer to the following URLs:
+
+* **Multi-GPU Models**: https://github.com/NVIDIA/multi-gpu-programming-models
+    - 2019 Recording of Multi GPU Programming Models GTC Tutorial: https://www.nvidia.com/en-us/on-demand/session/gtcsiliconvalley2019-s9139/
+    - 2020 Recording of Multi GPU Programming with MPI GTC Tutorial: https://www.nvidia.com/en-us/on-demand/session/gtcsj20-s21067/
+* **POWER+GPU Tutorial**: https://gitlab.version.fz-juelich.de/nval/sc19-tutorial-openpower
+    - SC19: https://sc19.supercomputing.org/presentation/?id=tut126&sess=sess189 
+    - SC18: https://sc18.supercomputing.org/?post_type=page&p=3479&id=tut156&sess=sess249 (broken)
+    - SC17: https://sc17.supercomputing.org/index.html%3Fpost_type=page&p=5407&id=tut149&sess=sess232.html 
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