backlight_control: add page (#8041)

* backlight_control: add page

* backlight_control: remove trailing whitespaces

* backlight_control: conjoin first two examples

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

* backlight_control: improve syntax

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

* backlight_control: improve syntax

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

* backlight_control: remove repeated example

Co-authored-by: Emily Grace Seville <emilyseville7cf@gmail.com>

pages/linux/backlight_control.md

@@ -0,0 +1,16 @@
+# backlight_control
+
+> Control a linux machine's backlight using percentage values.
+> More information: <https://github.com/Hendrikto/backlight_control>.
+
+- Increase/decrease the backlight by a specific percent count:
+
+`backlight_control {{+|-}}{{5}}`
+
+- Set the backlight strength to a specific percent count:
+
+`backlight_control {{90}}`
+
+- Print the help:
+
+`backlight_control`