Indicator LEDs as config (#10816)

* First pass

* Add config options to docs

* Update some wording

* Slight tidy up of backlight caps logic

* Init pin to correct state

* Move init location

* Reverse default state

tmk_core/common/led.h

@@ -15,8 +15,8 @@ You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef LED_H
-#define LED_H
+#pragma once
+
 #include "stdint.h"
 #include "stdbool.h"
 
@@ -52,5 +52,3 @@ void led_init_ports(void);
 #ifdef __cplusplus
 }
 #endif
-
-#endif