add changelog

changelog/unreleased/logging-to-file.md

@@ -0,0 +1,9 @@
+Enhancement: File Logging
+
+When running supervised, support for configuring all logs to a single log file:
+`OCIS_LOG_FILE=/Users/foo/bar/ocis.log MICRO_REGISTRY=etcd bin/ocis server`
+
+Supports directing log from single extensions to a log file:
+`PROXY_LOG_FILE=/Users/foo/bar/proxy.log MICRO_REGISTRY=etcd bin/ocis proxy`
+
+https://github.com/owncloud/ocis/pull/1816