Replace static image with inline rendered diagram
Replace static image with inline rendered diagram

Thanks to GitHubs recent addition of Mermaid support in GitHub-flavored
Markdown.

* [Include diagrams in your Markdown files with Mermaid](https://github.blog/2022-02-14-include-diagrams-markdown-files-mermaid/)
* [Mermaid](https://mermaid-js.github.io/mermaid/#/)

koppen/redmine_github_hook,koppen/redmine_github_hook