Options:
  --footer=STR             String to print as footer
  --footer-border[=STYLE]  Draw border around the footer section
                           [rounded|sharp|bold|block|thinblock|double|horizontal|vertical|
                            top|bottom|left|right|line|none] (default: line)
  --footer-label=LABEL     Label to print on the footer border
  --footer-label-pos=COL   Position of the footer label
                           [POSITIVE_INTEGER: columns from left|
                            NEGATIVE_INTEGER: columns from right][:bottom]
                           (default: 0 or center)

The default border type for footer is 'line', which draws a single
separator between the footer and the list. It changes its position
depending on `--layout`, so you don't have to manually switch between
'top' and 'bottom'

The 'line' style is now supported by other border types as well.
`--list-border` is the only exception.

This commit adds the `border-native` resulting in the following:

```
--tmux[=[center|top|bottom|left|right][,SIZE[%]][,SIZE[%]][,border-native]]
```

By default, when not specified, the `-B` flag is passed to the
`tmux popup-window` command such that no border is drawn around
the tmux popup window.

When the `border-native` option is present, the `-B` flag is omitted
and the popup window is drawn using the border style configured in
the tmux config file.

Fixes #4156

Signed-off-by: Andreas Auernhammer <github@aead.dev>
Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Fix #4001

Fix #3948

Close #3806

Known limitation:
* --height cannot be used

fzf --tmux center --bind 'enter:become:vim {}'