add CODEOWNERS for Cronvoy/Cronet sources (#1382)

Adding some new friends

Signed-off-by: Alan Chiu <achiu@lyft.com>

For an explanation of how to fill out the fields, please see the relevant section
in [PULL_REQUESTS.md](https://github.com/envoyproxy/envoy/blob/master/PULL_REQUESTS.md)

Description: add CODEOWNERS for Cronvoy/Cronet sources
Risk Level: low
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
[Optional Fixes #Issue]
[Optional Deprecated:]

CODEOWNERS

@@ -0,0 +1,5 @@
+# @envoyproxy/envoy-mobile-maintainers owns everything by default.
+
+# Cronet fork and Cronvoy sources + tests
+library/java/org/chromium/net @buildbreaker @goaway @DavidSchinazi @carloseltuerto
+test/java/org/chromium/net @buildbreaker @goaway @DavidSchinazi @carloseltuerto