Document hardware, pinout and I2C devices in a header comment of every device

Merge the old pinout comment blocks into the header and mark what each pin is used for.

mcu-clock-1.yaml

@@ -1,4 +1,18 @@
 ---
+# Hardware: M5Stack M5Stamp C3
+# Pinout:
+#   GPIO0   I2C SCL
+#   GPIO1   I2C SDA, BUTTON
+#   GPIO2   RGB
+#   GPIO4   DISPLAY CLOCK              -> tm1637_display (display tm1637 clk_pin)
+#   GPIO5   DISPLAY DIO                -> tm1637_display (display tm1637 dio_pin)
+#   GPIO6   GPIO
+#   GPIO7   GPIO
+#   GPIO8   GPIO
+#   GPIO9   GPIO (BUZZER?)             -> rtttl_out (output ledc)
+#   GPIO10  GPIO
+#   GPIO20  UART RX
+#   GPIO21  UART TX
 substitutions:
   device: clock-1
   name: Clock 1
@@ -25,21 +39,6 @@ packages:
   common: !include common/common.yaml
   ipv6_only: !include common/ipv6_only.yaml
 
-# GPIO21  UART TX
-# GPIO20  UART RX
-# GPIO0   I2C SCL
-# GPIO1   I2C SDA
-# GPIO2   RGB
-# GPIO1   BUTTON
-# GPIO4   DISPLAY CLOCK
-# GPIO5   DISPLAY DIO
-# GPIO6   GPIO
-# GPIO7   GPIO
-# GPIO8   GPIO
-# GPIO10   GPIO
-#
-# GPIO9   GPIO (BUZZER?)
-
 # https://github.com/granadaxronos/120-SONG_NOKIA_RTTTL_RINGTONE_PLAYER_FOR_ARDUINO_UNO/blob/master/RTTTL_PLAYER/songs.h
 api:
   actions: