Allow opening another TUI (e.g. text editor) temporarily before returning to watchbind

[fritzrehde]

I find myself longing for this feature in several cases where I quickly want to make an edit to some file that I am displaying in watchbind, and then return to watchbind. It would be cool if one could temporarily disable watchbind's TUI painting, execute a graphical TUI (e.g. text editor like vim), and return to watchbind.

[fritzrehde]

The functionality is there now, but I would still like to implement one feature: A smooth transition from watchbind's TUI to the child TUI (e.g. text editor). Currently, watchbind's TUI is hidden, then the regular command-line, from which watchbind was called, is shown for a split second, and only then is the TUI of the child command (text editor) shown. It would be nicer if the split second showcase of the command-line could be eliminated.

[fritzrehde]

The smooth (no return to user's terminal before launching child TUI) between watchbind's TUI and the child TUI has been implemented now. However, what is still missing is a similarly smooth transition from the child's TUI to watchbind's TUI, once the child's TUI terminates. Progress on implementing this will be tracked in #72.