add changelog for 0.4.0

CHANGELOG.md

 # Changelog
 
+## [0.4.0] - 2020-06-11
+
+* Replaced [local-storage
+  provisioner](https://open.greenhost.net/openappstack/local-storage) with
+  Rancher's [local-path
+  provisioner](https://github.com/rancher/local-path-provisioner)
+  * Patched the provisioner to work with Velero. The provisioner uses `local`
+    instead of `hostPath` Kubernetes volumes
+* Replaced RKE with K3s
+* Replaced prometheus-operator with Prometheus and Grafana manually installed
+* Added loki stack for log viewing
+* Added Velero for backups to s3-compatible storage
+* Added possibility to not install certain applications
+* Updated underlying applications:
+  * helm-operator uses Helm 3
+  * cert-manager chart 0.15.1
+  * local-path-provisioner chart 0.0.13
+  * nextcloud chart 0.2.3
+    * Nextcloud 17.0.0
+    * ONLYOFFICE 5.5.1
+      * Fixed: "prepare4shutdown" script is now run before shutdown
+  * Rocket.Chat chart 2.0.2
+    * [Patched RocketChat version](https://github.com/mrtndwrd/rocket.chat) at
+      3.2.2-096aa0023 because of [this ignored
+      PR](https://github.com/RocketChat/Rocket.Chat/pull/17377)
+  * Wordpress chart 0.1.2
+    * Moved repository to open.greenhost.net
+    * Updated WordPress to version 5.4.1
+    * Removed unused PVC
+  * Grafana chart 5.1.4
+  * Nginx chart 1.26.1
+  * Loki stack chart 0.36.2
+  * Prometheus chart 11.4.0
+
 ## [0.3.1] - 2020-03-18
 
 * Repair rocket chat installation