Auto highlight *Origin* and *Size* text on selection

[CaptainCooky]

This would be a nice little quality-of-life feature.

When selecting the values in the text fields of both the Origin and Size, it would be great if the pre-existing values were auto-highlighted.
This would be helpful when making complex selections.

e.g. When using the ctrl modifier to add to a selection, we could highlight the first block in a section, then click on an axis value and change the size value without selecting or deleting the existing text. A small thing, but it would greatly improve workflow.

[minecraftchloe]

Fantastic idea!