[Feature] Keep selection in highlight mode

[HakonHarnes]

Description
When using highlight mode (toggle_select_highlight), the text is de-selected after it has been highlighted. However, I often want to modify the color of the highlight (I use a specific coloring system) and I always have to re-select the highlight before applying the color change. Sometimes I also want to delete the highlight, e.g. if the selection was slightly off.

Solution
After a highlight has been made, don't de-select the text. This way, it's simple to change or delete the highlight without having to manually re-select the highlight every time.