[Feature request] Allow resizing the screenshot area before making the screenshot

[matthijskooijman]

Currently, when making an area screenshot, you drag an area and the screenshot is made right away.

Some other screenshot applications support a multi-stage procedure: First you drag an area, which is shown on-screen and can be subsequently edited (moved or resized). When you are happy with the selected area, you press enter or click a button to actually make the screenshot. This approach makes it easier to select the right area, especially when you want to capture something where the bounds are not in the corners, so you have to somewhat guess where to start the screenshot (e.g. where to click first).

It might be useful to offer something similar for this extension too.

For example, here's how it looks using Flameshot, after dragging an initial area:

This also has a bunch of buttons for different actions around the screenshot area, which could work for this extension too, but might be hard to combine with the existing UI flow.