GFM like admonitions/callouts

### Have you read the Contributing Guidelines on issues?

- [X] I have read the [Contributing Guidelines on issues](https://github.com/facebook/docusaurus/blob/main/CONTRIBUTING.md#reporting-new-issues).

### Motivation

Github is experimenting with adding admonition/callout support to GFM. When and if the solution stabilises it would be nice to make docusaurus compatible with this solution as this would make it easier to reuse markdown content that was initially written for github. Another point for it is to lower the learning curve as GFM is an industry standard.

From this [comment](https://github.com/facebook/docusaurus/issues/7344#issuecomment-1118535948) I can see that there are known issues with current admonition implementation and there are plans to fork it #6246.

Two examples of this feature:

> **Note**
> At time of creation GFM callouts is an experimental feature and is discussed [here](https://github.com/github/feedback/discussions/16925)

> **Warning**
> GFM callouts currently only support `Note`| `Warning` variations while docusaurus [docs](https://docusaurus.io/docs/markdown-features/admonitions) mention support for `note` | `tip` | `info` | `caution` | `danger`

### Self-service

- [ ] I'd be willing to do some initial work on this proposal myself.