Add save button for new connection

[JannemanDev]

Motivation

When you want to make a new connection and fill in some (but not necessarly all) fields you can't temporailty save it and complement it later on. You can only choose Connect which is not always what you want.

Suggestion: add a save button next to connect.

[oceanlvr]

It's a great suggestion, we'll consider it possible.

[GuryYu]

And edit connection needs save button too.

[ysfscream]

Thanks for your feedback. It is now available at: https://github.com/emqx/MQTTX/releases/tag/v1.9.10. Welcome to try it.