Add the ability to change focus automatically when process finishes

[rickstaa]

I just noticed that @nat-chan created a very useful feature in his fork. This new feature automatically switches focus to the finished window. I think this would be good. I, however, think it should not be the default as it is currently in @nat-chan's branch.

Proposal

My Idea is to pull the changes of @nat-chan into my fork and modify them slightly such that user has two ways to monitor a pane:

• prefix + m: The regular pane monitor option.
• prefix + alt + m: Now the pane is monitored, and the focus is returned to the pane when it finishes.

Alternatively, we can of course also use a tmux-option to change this behaviour, but I think the above method would allow users to decide on a pane basis whether the want to return the focus. @ChanderG and @bruno- what do you think about this new feature?

[ChanderG]

Sounds good - per pane selection like you mention seems better.

[rickstaa]

@ChanderG great I will start working on it after we resolved #14.

[rickstaa]

This feature is added in #17