Add CREDITS.md file

This file lists all code contributors to Ibex as of today, and
acknowledges the great work done by the PULP team at ETH Zürich.

The names in this file have been compiled from the git history, and all
authors which are named in the individual source files.

CREDITS.md

@@ -0,0 +1,44 @@
+Credits
+=======
+
+Ibex has originally been developed by the PULP team at ETH Zürich and
+University of Bologna under the name Zero-riscy. In December 2018, Ibex has
+been contributed to lowRISC who is maintaining and advancing the design since
+then.
+
+Throughout the years, Ibex has seen contributions from many people and we at
+lowRISC are very thankful for all of them. This file lists the many people who
+contributed to what is called Ibex today. If you made a contribution to Ibex
+in the form of source code, bug reports, testing, marketing, or any other form,
+please feel free to open a pull request to get your name added to this file.
+
+- Alex Bradbury
+- Andreas Traber
+- Antonio Pullini
+- Eunchan Kim
+- Florian Zaruba
+- Francesco Conti
+- Germain Haugou
+- Igor Loi
+- Ioannis Karageorgos
+- Markus Wegmann
+- Ivan Ribeiro
+- Matthias Baer
+- Michael Gautschi
+- Michael Schaffner
+- Nils Graf
+- Noah Huesser
+- Pasquale Davide Schiavone
+- Philipp Wagner
+- Pirmin Vogel
+- Rahul Behl
+- Rhys Thomas
+- Renzo Andri
+- Robert Schilling
+- Scott Johnson
+- Stefan Wallentowitz
+- Sven Stucki
+- Tao Liu
+- Tobias Wölfel
+- Tom Roberts
+- Udi Jonnalagadda