top: Add CONTRIBUTORS.md file

We add CONTRIBUTORS.md file to provide a list of individuals and
organizations actively contributing to the OpenSBI project.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
diff --git a/COPYING.BSD b/COPYING.BSD
index 17ee3ae..26972c8 100644
--- a/COPYING.BSD
+++ b/COPYING.BSD
@@ -1,7 +1,8 @@
 The 2-Clause BSD License
 SPDX short identifier: BSD-2-Clause
 
-Copyright (c) 2019 Western Digital Corporation or its affiliates.
+Copyright (c) 2019 Western Digital Corporation or its affiliates and other
+contributors.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
@@ -22,4 +23,3 @@
 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-