Create and maintain release notes

[christianbrb]

Analysis

Current State

Currently, the release overview just shows the release number and commit.

Problem

For me, it is very difficult to find out which changes/PRs have been released and therefore run the nightly jobs.

I would like to see, which change/PR has been released to master and is running the nightly job.

Solution

Potential solutions

• Manually add each PR to the release notes (see an example)
• Using https://chronicler.starchartlabs.org/
• Using https://github.com/toolmantim/release-drafter
• ... any other solution, which solves the problem

[christianbrb]

#261 does not seem to have fixed this issue. At least I don't find details about the release within https://github.com/raiden-network/scenario-player/releases/tag/v0.3.9