[Enhancement] Add mention of Zed support

### Before submitting

- [x] I am using the latest version of Quarkdown.
- [x] I have checked the [wiki](https://quarkdown.com/wiki) to confirm this feature doesn't already exist.
- [x] I have searched existing [issues](https://github.com/iamgio/quarkdown/issues) for duplicates.

### Description

Hi everyone !

I made a simple [Zed](zed.dev) extension to support Quarkdown using the LSP + an existing tree-sitter project.
So far it's pretty basic but it works nicely. It's still a [PR in review](https://github.com/zed-industries/extensions/pull/5822) for now but I think it should be approved anytime soon.

I'm suggesting adding a mention of this in the readme just so it can be found easily for people using Zed.

### Proposed syntax or behavior

```markdown

```

### Additional context

_No response_

Start by locating the repository README and checking where editor or integration support is described. Add a discoverable mention of the Quarkdown Zed extension, linking to the extension or its review PR, and confirm the wording renders correctly and accurately reflects its current review status.

Written by the indexing model from the issue text.