Describing resources

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

When you have many resources you might be confused as to what a resource _is_. Currently the only description we have is the name itself, which is quite limited in terms of what you can write and ideally shouldn't be too long.

### Describe the solution you'd like

Some way to add a description to a resource that's visible in the dashboard - maybe as a tooltip.

```c#

var fileWatcher = builder.AddExecutable("file-watcher", dir)
.WithDescription($"Watches for files in {dir} and when anything changes, invalidates the {whatever} cache and triggers a regeneration.")
```

Not entirely sure how or where to view these descriptions, but this issue came to me as I was wondering what a resource did and noticed there is no way to describe a resource in this way.

### Additional context

_No response_