Add basic KMSCON support (closes #886)

It's not perfect yet, but at least it works!

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

res/config.ini

@@ -316,8 +316,9 @@ service_name = ly
 # Session log file path
 # This will contain stdout and stderr of Wayland sessions
 # By default it's saved in the user's home directory
-# Important: due to technical limitations, X11 and shell sessions aren't supported, which
-# means you won't get any logs from those sessions.
+# Important: due to technical limitations, X11, shell sessions as well as
+# launching session via KMSCON aren't supported, which means you won't get any
+# logs from those sessions.
 # If null, no session log will be created
 session_log = .local/state/ly-session.log