Add default (mock) Contexthub HAL 1.1 impl

Current implementation exposes a mock context hub, but with no nanoapps.

Bug: 135951924
Test: compile only (will be covered by VTS in a follow-up)
Change-Id: I7a13527f303ce1bcacac8c6be9f081b0838cdc68
diff --git a/contexthub/1.1/default/OWNERS b/contexthub/1.1/default/OWNERS
new file mode 100644
index 0000000..90c2330
--- /dev/null
+++ b/contexthub/1.1/default/OWNERS
@@ -0,0 +1,3 @@
+arthuri@google.com
+bduddie@google.com
+stange@google.com