cronet: jarjar androidx inside cronet

To make sure cronet's androidx does not conflict with anything.

Test: atest CronetApiTest
Change-Id: Iad05e489a82a27c2cb7be1e115359efec6bef907
diff --git a/Cronet/jarjar-rules.txt b/Cronet/jarjar-rules.txt
new file mode 100644
index 0000000..7111ebc
--- /dev/null
+++ b/Cronet/jarjar-rules.txt
@@ -0,0 +1,3 @@
+rule androidx.** com.android.cronet.@0
+rule android.support.** com.android.cronet.@0
+