CI: add sway compositor to CI tests, to prepare for better Wayland testing

closes: #17162

Signed-off-by: Foxe Chen <chen.foxe@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/ci/setup-sway.sh b/ci/setup-sway.sh
new file mode 100644
index 0000000..060b7f9
--- /dev/null
+++ b/ci/setup-sway.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+set -e
+
+# Using a systemd user service doesn't work because it seems like github actions
+# doesn't support user sessions? Just run sway in the background and disown it.
+WLR_BACKENDS=headless sway &
+disown