README better examples

[deter]

"You could amend your readme to explain that one needs to set up rounded corners in picom.conf, set borders to 0 in the i3 config, that the picom corner radius should match `border-radius and give a short example json-file like

{
  "border-radius": 10, 
  "border-width": 5, 
  "border-rgba": "FFFF00FF" 
}

might seem obvious, but still...."

u/r_wraith on reddit

[arnavgr]

how do i reduce the size of the border?

[deter]

@arnavgr
./xborders --border-width=1