Dual-kawase blur no longer requires picom-git or experimental backends

[ds196]

Hello,

Been using a Plasma-i3 configuration for a long time now with a configuration from this repo and I love it. I wanted to make a few comments to update the instructions a little bit with respect to picom.

1. the default configuration is now located at /etc/xdg/picom.conf instead of /etc/xdg/picom.conf.example

2. Dual-kawase blur is now included in extra/picom rather than just picom-git in AUR, and no longer requires using --experimental-backends (Here is my startup line for picom: exec_always --no-startup-id picom -bc --no-fading-openclose --backend glx --blur-method dual_kawase --config $HOME/.config/picom.conf)

Man page for picom can be found here.
I'm running picom 11.2-1 from extra/picom