[FR] Alternative Group Name Display

[Bengt Brodersen]

Is your feature request related to a problem? Please describe.
The display of all groups as headers is annoying.

Describe the solution you'd like
Display group name as border label see example below:

 echo "alias alias1\nexternal-command value2" | fzf --layout=reverse \
   --with-nth=2 \
   --border=bottom --border-label-pos=1 \
   --bind="focus:transform-border-label(echo ' '{1}' ')"

Display selected group as prompt prefix see example below:

echo "alias alias1\nexternal-command value2" | fzf --layout=reverse \
  --with-nth=2 \
  --bind=",:reload(echo alias alias1)+transform-prompt(echo alias'> ')" \
  --bind=".:reload(echo external-command value2)+transform-prompt(echo external-command'> ')"