FAQ: Add directions for mod-key passthrough

FAQ.md

@@ -1,5 +1,18 @@
 # FAQ
 
-### How can I run wayvnc in headless mode/over an ssh session?
+*Q: How can I run wayvnc in headless mode/over an SSH session?*
 
-Set the environment variables WLR_BACKENDS=headless and WLR_LIBINPUT_NO_DEVICES=1 before starting sway, then run wayvnc as normal.
+A: Set the environment variables `WLR_BACKENDS=headless` and
+`WLR_LIBINPUT_NO_DEVICES=1` before starting sway, then run wayvnc as normal.
+
+*Q: How can I pass my mod-key from Sway to the remote desktop session?*
+
+A: Create an almost empty mode in your sway config. Example:
+```
+mode passthrough {
+	bindsym $mod+Pause mode default
+}
+bindsym $mod+Pause mode passthrough
+```
+This makes it so that when you press $mod+Pause, all keybindings, except the one
+to switch back, are disabled.