And if you start a markdown codeblock like

    ```mermaid
    graph TD;
      A-->B
    ```

Many things that support markdown (e.g. github, gitlab, typora, ...) will render the resulting graph.

That features is also a feature Mermaid/Markdown renderers have borrowed from existing uses of PlantUML. You've been able to embed PlantUML in a Markdown block in Gitlab (and have it rendered inline as an image) since before MermaidJS ever existed. Github's embedded MermaidJS feature is years late.

unfortunately, you need a PlanetUML server when using a self hosted gitlab install.

running directly in the browser is, imho, the best feature of mermaidjs