Add changelog for 304
This MR was automatically created from CI, https://gitlab.com/gitlab-org/gitter/gitter-android-app/-/jobs/169659494
We copied CURRENT_VERSION.txt
-> 304.txt
This MR was automatically created from CI, https://gitlab.com/gitlab-org/gitter/gitter-android-app/-/jobs/169659494
We copied CURRENT_VERSION.txt
-> 304.txt