Ensure KWallet auto-login

This is required to avoid Brave requesting access to KWallet on first
launch.

README.md

···
 ```bash
 paru -S \
   swayidle \
+  kwallet-pam \
   fprintd \
   yazi \
   btop \
···
 
 ##### Brave
 
-My preferred browser:
+My preferred browser. It uses KWallet for storing passwords (requires wallet password to match user password).
 
 ```bash
 paru -S brave-bin

dot_config/niri/config.kdl

···
 
     spawn-sh-at-startup "swww-daemon" // Wallpaper daemon
     spawn-sh-at-startup "swww img ~/.config/niri/background.jpg" // Set wallpaper
+    spawn-sh-at-startup "/usr/lib/pam_kwallet_init" // Unlock KWallet
 
     prefer-no-csd // Disable program decorations
     screenshot-path null // Disable screenshot saving