[Keyboard] Add Meck TKL handwired (#15533)

* Add meck_tkl

* Fix configuration and pin assignment

* Rellocate A10 pin, as it is used by the USB DFU bootloader

* Add volume and media keys to the function keys layer

* Rellocate source files to the handwired keyboards folder and add documentation

* Review changes for PR
- Improve LAYOUT macro to match the keyboard layout.
- Use "kxy" as pin names on the LAYOUT macro.
- Remove unused mcuconf.h and halconf.h.
- Fix README.

* Improve layout macro naming

keyboards/handwired/meck_tkl/rules.mk

@@ -0,0 +1,16 @@
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
+MOUSEKEY_ENABLE = yes       # Mouse keys
+EXTRAKEY_ENABLE = yes       # Audio control and System control
+CONSOLE_ENABLE = yes        # Console for debug
+COMMAND_ENABLE = no         # Commands for debug and configuration
+NKRO_ENABLE = yes           # Enable N-Key Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
+AUDIO_ENABLE = no           # Audio output
+AUDIO_SUPPORTED = no
+BACKLIGHT_SUPPORTED = no
+
+DEFAULT_FOLDER = handwired/meck_tkl/blackpill_f401