waybar: Add keepawake module

Shows if the pc will not automatically turn off screen or suspend.
Figures this out by checking for `swayidle` process, so that is
required. Turns on suspend again on click, and uses voidlinux `sv` user
service for it, so those have to be set up.

desktop/.config/waybar/style.css

@@ -18,6 +18,10 @@ window#waybar.hidden {
     opacity: 0.2;
 }
 
+.hidden {
+    opacity: 0;
+}
+
 #tags button {
     font-size:17px;
     font-weight:900;
@@ -70,6 +74,7 @@ window#waybar.hidden {
 #custom-wireguard,
 #custom-events,
 #custom-vidl,
+#custom-keepawake,
 #custom-media {
     padding: 0 5px;
     margin: 0 5px;