Compilation fixes for handwired/concertina/64key (#11987)

* concatenate config.h to 64key directory

* move rules.mk to 64key directory

This commit makes the firmware actually compile.

* insert complete rules.mk contents

Conforms the file to QMK's template.

* move info.json to 64key directory

* remove concertina.h

This file no longer serves a purpose now that everything is in the 64key directory.

* complete 64key readme.md

Conforms the file more to QMK's template.

keyboards/handwired/concertina/64key/rules.mk

@@ -0,0 +1,25 @@
+# Written for a Pro Micro. The keyboard case is compatible with much else.
+# MCU name
+MCU = atmega32u4
+
+# Bootloader selection
+BOOTLOADER = caterina
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = lite     # Virtual DIP switch configuration
+MOUSEKEY_ENABLE = yes       # Mouse keys
+EXTRAKEY_ENABLE = yes       # Audio control and System control
+CONSOLE_ENABLE = no         # Console for debug
+COMMAND_ENABLE = no         # Commands for debug and configuration
+# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
+SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
+# if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+NKRO_ENABLE = no            # USB Nkey Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
+BLUETOOTH_ENABLE = no       # Enable Bluetooth
+AUDIO_ENABLE = no           # Audio output
+
+TAP_DANCE_ENABLE = yes