[Meta] Enable GitHub Discussions.

[RokeJulianLockhart]

My rationale is available at https://github.com/8go/matrix-commander/issues/68#issue-1237645245. However, specifically here, I would like to ask whether nested HTML and Markdown are correctly rendered (https://mermaid.js.org/syntax/flowchart.html#markdown-formatting versus https://mermaid.js.org/syntax/flowchart.html#unicode-text, the latter supporting HTML).

For instance:

```mermaid
flowchart TD
    node_s9gvm9["`
        **Heading**
        Body text.
    `"]
    node_s9gyel["
        <b>Heading</b>
        Body text.
    "]
```

[bpruitt-goddard]

I enabled discussions on the repo, feel free to post your question over there and close this issue. Thanks for the suggestion!