Add some feedback while benchmark is running

[Dr-Noob]

Something that makes the user understand that computing is taking place.

For example, a progress bar, like:

|███████████████ | 50%
|████████████████████████████████| 100%

or a blinking cursor like this function does:

spin() {
   local -a marks=( '/' '-' '\' '|' )
   while [[ 1 ]]; do
     printf '%s\r' "${marks[i++ % ${#marks[@]}]}"
     sleep 0.1
   done
 }

This would require adding an additional thread in main