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-kitchen.yaml

@@ -1,4 +1,21 @@
 ---
+# Hardware: M5Stack ATOM Lite + ATOM Hub Switch
+# Pinout:
+#   GPIO1   UART0 TX
+#   GPIO3   UART0 RX
+#   GPIO12  IR
+#   GPIO19  Relay2
+#   GPIO21  I2C1 SCL                   -> i2c (i2c scl)
+#   GPIO22  Relay1                     -> power_supply1 (power_supply)
+#   GPIO23  RS485 Tx
+#   GPIO25  I2C1 SDA - red             -> i2c (i2c sda)
+#   GPIO26  I2C0 SDA - white
+#   GPIO27  NEO 1x
+#   GPIO32  I2C0 SCL
+#   GPIO33  RS485 Rx
+#   GPIO39  BUTTON                     -> Status Button (binary_sensor gpio)
+# I2C:
+#   0x40  pca9685_hub1 (pca9685)
 substitutions:
   device: kitchen
   name: Kitchen
@@ -41,21 +58,6 @@ packages:
 api:
   reboot_timeout: 300s
 
-# PINOUTS: M5ATOM+Atom Hub Switch
-# IR        G12
-# NEO       G27 1x
-# BUTTON    G39
-# I2C0 SDA  G26 - white
-# I2C0 SCL  G32
-# I2C1 SDA  G25 - red
-# I2C1 SCL  G21
-# UART0 RX  G3
-# UART0 TX  G1
-# RS485 Rx  G33
-# RS485 Tx  G23
-# Relay1    G22
-# Relay2    G19
-
 i2c:
   # - id: i2c0
   #   sda: 26