[Docs] Update how_keyboards_work.md (#6528)

* Update how_keyboards_work.md

bridged the gap between scancodes and keycodes, the doc didn't make the distinction and was ambiguous.

* Update docs/how_keyboards_work.md

Co-Authored-By: Drashna Jaelre <drashna@live.com>

* Update docs/how_keyboards_work.md

fix typo

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>

docs/how_keyboards_work.md

@@ -33,7 +33,11 @@ The firmware does not send actual letters or characters, but only scancodes.
 Thus, by modifying the firmware, you can only modify what scancode is sent over
 USB for a given key.
 
-## 3. What the Operating System Does
+## 3. What the Event Input/Kernel Does
+
+The *scancode* is mapped to a *keycode* dependent on the keyboard [60-keyboard.hwdb at Master](https://github.com/systemd/systemd/blob/master/hwdb/60-keyboard.hwdb). Without this mapping, the operating system will not receive a valid keycode and will be unable to do anything useful with that key press.
+
+## 4. What the Operating System Does
 
 Once the keycode reaches the operating system, a piece of software has to have
 it match an actual character thanks to a keyboard layout. For example, if your