README.md: Add Coding Style section

Change-Id: I71056641fed2ba8c5e7d13f83c48772d1acd7bd1

README.md

diff --git a/README.md b/README.md
index b604e0d..b5cdfe1 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,15 @@
 Eclipse before rebuilding.
 
 
+Code Style
+----------
+
+Java code in Gitiles follows the [Google Java Style Guide]
+(https://google.github.io/styleguide/javaguide.html) with a 100-column limit.
+
+CSS in Gitiles follows the [SUIT CSS naming conventions]
+(https://github.com/suitcss/suit/blob/master/doc/naming-conventions.md).
+
 Code Review
 -----------