doc: split up yambar-modules

Closes #15

doc/yambar-modules-backlight.5.scd

@@ -0,0 +1,46 @@
+yambar-modules-backlight(5)
+
+# NAME
+backlight - This module reads monitor backlight status
+
+# DESCRIPTION
+This module reads monitor backlight status from
+_/sys/class/backlight_, and uses *udev* to monitor for changes.
+
+# TAGS
+
+[[ *Name*
+:[ *Type*
+:[ *Description*
+|  brightness
+:  range
+:  The current brightness level, in absolute value
+|  percent
+:  range
+:  The current brightness level, in percent
+
+# CONFIGURATION
+
+[[ *Name*
+:[ *Type*
+:[ *Req*
+:[ *Description*
+|  name
+:  string
+:  yes
+:  The backlight device's name (one of the names in */sys/class/backlight*)
+
+# EXAMPLES
+
+```
+bar:
+  left:
+    - backlight:
+        name: intel_backlight
+        content:
+          string: {text: "backlight: {percent}%"}
+```
+
+# SEE ALSO
+
+*yambar-modules*(5), *yambar-particles*(5), *yambar-tags*(5), *yambar-decorations*(5)