Implements delayed area screenshots

Hi the feature similar to described in #43 (closed) was useful to me so I implemented it.

Now it is possible to take screenshot of area after delay - delay countdown is started after user selects rectangle on screen. Works both with interactive mode and command line mode (--area and --delay are now allowed together). Implementation is simple - after selecting rectangle we look if there is delay configured and if yes then we wait for delayed amount of time. I've done basic regression of a

If you would want this feature then translations needs to be cleared from phase "Conflicting options: --window and --area should not be used at the same ". Also CI fails and I don't really understand why.