Document new useConnection and onConnectEnd params

[moklick]

Code of Conduct

• [X] I have read and agree to the xyflow contributor Code of Conduct

Which site are you suggesting a change for?

reactflow.dev

What content is affected by this change?

useConnection, onConnectEnd and onReconnectEnd

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

docs

Additional information

No response