Use chromium style for yapf

Change-Id: Ib7fc352a6da44bbefa78c571795d615881a08dba
diff --git a/.style.yapf b/.style.yapf
new file mode 100644
index 0000000..c0975d8
--- /dev/null
+++ b/.style.yapf
@@ -0,0 +1,4 @@
+[style]
+# While normally Pigweed uses PEP8, recipes code frequently moves between
+# repos. This movement is made easier if we stick to Chromium style here.
+based_on_style = chromium