update changelog

Author: jcodybaker

CHANGELOG.md

@@ -19,6 +19,8 @@
   [[GH-143]](https://github.com/digitalocean/csi-digitalocean/pull/143)
 * Fix race in snapshot integration test.
   [[GH-146]](https://github.com/digitalocean/csi-digitalocean/pull/146)
+* Add tagging support for Volume snapshots via the new `--do-tag` flag
+  [[GH-145]](https://github.com/digitalocean/csi-digitalocean/pull/145)
 
 ## v1.0.0 - 2018.12.19