Upstream communication policy.

Upstream communication policy describe a way we communicate with
upstream projects. It doesn't cover all cases because upstreams are
different (some use local files/tarballs instead of VCS) but it aims
to cover common cases and principles.

Related to https://git.ostc-eu.org/OSTC/OHOS/governance/ip-policy/-/issues/17



Signed-off-by: Pavel Zhukov <pavel.zhukov@huawei.com>