[Keyboard] Added D48 keyboard (#8548)

* [Keyboard] Added D48 keyboard.

* Updated README.

* Cleanups.

* Moved d48 to handwired/

* Added link to build process album.

* Coding conventions cleanups.

* Added DS1307 RTC!

* Minor cleanups.

* Apply suggestions from code review

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

* Minor refactoring.

* Readme fix.

* Moved leftover keymap-specific code from keyboard space into keymap.

* Added encoder button pins to extra matrix row.

* Updated README, updated pinout & cleaned up the glcdfont

* Apply suggestions from code review

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

* Update config.h

* Apply suggestions from code review

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Added default keymap. Refactored existing keymap.

* Update keyboards/handwired/d48/README.md

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Apply suggestions from code review

Co-Authored-By: Joel Challis <git@zvecr.com>

* Minor alignment fix.

* Update keyboards/handwired/d48/glcdfont_d48.c

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Changes as per PR.

* Apply suggestions from code review

Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

keyboards/handwired/d48/rules.mk

@@ -0,0 +1,22 @@
+# MCU name
+MCU = STM32F303
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = no   # Virtual DIP switch configuration
+MOUSEKEY_ENABLE = no    # Mouse keys
+EXTRAKEY_ENABLE = yes   # Audio control and System control
+CONSOLE_ENABLE = yes    # Console for debug
+COMMAND_ENABLE = no     # Commands for debug and configuration
+SLEEP_LED_ENABLE = no   # Breathing sleep LED during USB suspend
+NKRO_ENABLE = yes       # USB Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+BACKLIGHT_ENABLE = no   # Enable keyboard backlight functionality
+AUDIO_ENABLE = yes
+USE_I2C = no
+RGBLIGHT_ENABLE = yes
+ENCODER_ENABLE = yes
+OLED_DRIVER_ENABLE = yes
+UNICODE_ENABLE = yes
+
+SRC += ds1307.c taphold.c