Improve docs on how to set up different Mousebuttons for panOnDrag

### Code of Conduct

- [x] I have read and agree to the xyflow contributor [Code of Conduct](https://github.com/xyflow/web/blob/main/CODE_OF_CONDUCT.md)

### Which site are you suggesting a change for?

svelteflow.dev

### What content is affected by this change?

-

### What part(s) of the article would you like to see updated?

-

### Additional information

_No response_