Josef Schabasser

[slim] wrong base in readme

1

Hi! The readme is wrong about the `slim` images: they are based on Debian Stretch. ``` $ docker run keymetrics/pm2:12-slim cat /etc/debian_version 9.12 ``` keymetrics/pm2:12-slim Dockerfile: https://github.com/keymetrics/docker-pm2/blob/999851207955a4a6ffb2ca50f4e2900b35e2abc0/tags/12/slim/Dockerfile#L1 node:12-slim Dockerfile: https://github.com/nodejs/docker-node/blob/fdd2b251827817ac7bb4f0b2b082483abff8ea77/12/stretch-slim/Dockerfile#L1...

## Pre-Submission Checklist - [X] Opened an issue discussing these changes before opening the PR - [ ] Run the tests via `bash test/test.sh` - [ ] Included comprehensive and...

## New issue checklist - [X] I have read all of the [`README`](https://github.com/nimiq-network/core/blob/master/README.md) - [X] I have searched [existing issues](https://github.com/nimiq-network/core/issues?q=is%3Aissue+sort%3Acreated-desc) and **this is not a duplicate**. ### General information -...