Give the Bubbles team owners on WMShell multivalentTests

Bug: none
Test: treehugger
Change-Id: I3f339248a31e0ac7764856861de3a1581d46b41d
diff --git a/libs/WindowManager/Shell/multivalentTests/OWNERS b/libs/WindowManager/Shell/multivalentTests/OWNERS
new file mode 100644
index 0000000..24c1a3a
--- /dev/null
+++ b/libs/WindowManager/Shell/multivalentTests/OWNERS
@@ -0,0 +1,4 @@
+atsjenk@google.com
+liranb@google.com
+madym@google.com
+