[Keyboard] PCB Ruler updates (#6584)

* Move default keymap's rules to keyboard level

* Concatenate the two sets of rules

This sets CONSOLE_ENABLE to no, which was being set at the keymap level.

* Wrap the USB Device Description in quotes

Some preventative maintenance. The firmware for the_ruler can't be compiled without this change if `CONSOLE_ENABLE = yes` because this string has a comma, which gets picked up as two arguments by the Command code, instead of one as it should be.

* Linting

- remove firmware size impacts
- remove trailing white space
- visual alignment of rules

* Use QMK's pre-loaded default rules for atmega32u4

* Update readme

- markdown formatting
- update Hardware Availability link (Maple Computing's site has disappeared)
- update Docs links

* Update header files to use #pragma once

keyboards/the_ruler/the_ruler.h

@@ -1,5 +1,4 @@
-#ifndef THERULER_H
-#define THERULER_H
+#pragma once
 
 #include "quantum.h"
 
@@ -7,5 +6,3 @@
     K00, K01, K02, K03, K04, K05 ) { \
     { K00, K01, K02, K03, K04, K05 }  \
 }
-
-#endif