[Keyboard] add handwired/oem_ansi_fullsize (#13857)

* Add new keyboard oem_ansi_fullsize

* clang-fmt

* Update keyboards/handwired/oem_ansi_fullsize/rules.mk

Co-authored-by: Joel Challis <git@zvecr.com>

* Update keyboards/handwired/oem_ansi_fullsize/readme.md

Co-authored-by: Joel Challis <git@zvecr.com>

* update info.json using qmk c2json

* update info.json

* move diagram to readme

* add matrix cols/rows to info.json

* fixup! add matrix cols/rows to info.json

* rename layout, fix block comment

* s/ansi_fullsize/fullsize_ansi/g

Co-authored-by: Joel Challis <git@zvecr.com>

keyboards/handwired/oem_ansi_fullsize/rules.mk

@@ -0,0 +1,24 @@
+# MCU name
+MCU = at90usb1286
+
+# Bootloader selection
+BOOTLOADER = halfkay
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = lite     # Virtual DIP switch configuration
+MOUSEKEY_ENABLE = no        # 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
+
+LAYOUTS = fullsize_ansi