Add design documentation.

Change-Id: I22abf525f9389cf942c0b66b8c34c5446dd8d306
Reviewed-on: https://swiftshader-review.googlesource.com/5431
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
diff --git a/README.md b/README.md
index be93bca..5eca60b 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@
 Documentation

 -------------

 

-See (docs/Index.md)[docs/Index.md].

+See [docs/Index.md](docs/Index.md).

 

 Contact

 -----------