Release 0.15.5

# History

## 0.15.5

Install/update via the bootstrap script:

```shell
wget https://raw.githubusercontent.com/dokku/dokku/v0.15.5/bootstrap.sh
sudo DOKKU_TAG=v0.15.5 bash bootstrap.sh
```

### New Features

- #3511: @josegonzalez Add json output to config:export

### Documentation

- #3510: @josegonzalez Remove SPONSORS doc in favor of OpenCollective
- #3509: @Neamar Missing space in markdown formatting
- #3507: @renestalder Fix GitLab CI examples

debian/control

@@ -1,5 +1,5 @@
 Package: dokku
-Version: 0.15.4
+Version: 0.15.5
 Section: web
 Priority: optional
 Architecture: amd64