Add option to move backspace button to the left

**Is your feature request related to a problem? Please describe.**
I'm always frustrated when I need to reach the 0 bottom with my right thumb that it's quite far.

**Describe the solution you'd like**
Adding an option to move the backspace button completely to the left (below 1) and moving the 0 to below the 2 and the dot to below the 3 buttons.

**Describe alternatives you've considered**
I'm coming from a Samsung Galaxy phone and am frustrated about the layout of the default calculator on my pixel, that's why I've switched to OpenCalc. I assume others will have this as well. Therefore, it's better to have it as a customization option instead of something fixed.

**Additional context**
The layout of the Samsung Calculator