Add login & logout script support

Signed-off-by: AnErrupTion <anerruption@disroot.org>

res/config.ini

@@ -1,11 +1,11 @@
 # The active animation
-# none   -> Nothing (default)
+# none   -> Nothing
 # doom   -> PSX DOOM fire
 # matrix -> CMatrix
 animation = none
 
 # Stop the animation after some time
-# 0 -> Run forever (default)
+# 0 -> Run forever
 # 1..2e12 -> Stop the animation after this many seconds
 animation_timeout_sec = 0
 
@@ -112,6 +112,18 @@ lang = en
 # Load the saved desktop and username
 load = true
 
+# Command executed when logging in
+# If null, no command will be executed
+# Important: the code itself must end with `exec "$@"` in order to launch the session!
+# You can also set environment variables in there, they'll persist until logout
+login_cmd = null
+
+# Command executed when logging out
+# If null, no command will be executed
+# Important: the session will already be terminated when this command is executed, so
+# no need to add `exec "$@"` at the end
+logout_cmd = null
+
 # Main box horizontal margin
 margin_box_h = 2