[mcp3204] differential mode support (#5634)

* Update mcp3204.md with diff mode from 

This PR adds documentation for the new differential mode feature for the MCP3204/MCP3208 ADC components.

* Update content/components/sensor/mcp3204.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update content/components/sensor/mcp3204.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update content/components/sensor/mcp3204.md

Channels typo

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* Clean up

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>

Author: 3 people

content/components/sensor/mcp3204.md

@@ -58,19 +58,48 @@ sensor:
     id: solar_voltage
     number: 0                     # MCP3204 pin number
 
-# In case MCP3208 is used. you can specify pin number > 4
+  # In case MCP3208 is used, you can specify pin number > 4
   - platform: mcp3204             # Attached to pin 7 of the MCP3208.
     id: supply_voltage
     number: 7                     # MCP3208 pin number
+
+  # Measures difference between CH0 (IN+) and CH1 (IN-)
+  - platform: mcp3204             # Differential pair on pins 0-1.
+    id: thermocouple_voltage
+    number: 0
+    diff_mode: true
 ```
 
 ### Configuration variables
 
 - **mcp3204_id** (**Required**, [ID](/guides/configuration-types#id)): The id of the parent MCP3204 component.
-- **number** (**Required**, int): The pin number of the MCP3204
-- **update_interval** (*Optional*, [Time](/guides/configuration-types#time)): The interval to check the sensor. Defaults to `60s`.
+- **number** (**Required**, int): The pin to measure on the MCP3204/MCP3208
+- **update_interval** (*Optional*, [Time](/guides/configuration-types#time)): The interval to check the sensor.
+  Defaults to `60s`.
+- **diff_mode** (*Optional*, boolean): Enable differential mode measurement. Defaults to `false`.
 - All other options from [Sensor](/components/sensor).
 
+## Operating Modes
+
+The MCP3204/3208 supports two input configurations:
+
+### Single-Ended Mode (default)
+
+Each channel measures voltage independently relative to ground. The MCP3204 provides 4 channels,
+and MCP3208 provides 8 channels. This is the default operating mode when `diff_mode` is not
+specified or set to `false`.
+
+### Differential Mode
+
+When `diff_mode: true`, channel pairs measure the voltage difference between two inputs (IN+ and
+IN-). Specify the positive input channel number with the `number` parameter. The next sequential
+channel automatically becomes the negative input (IN-).
+
+Available differential pairs:
+
+- MCP3204: 2 pairs (CH0/CH1, CH2/CH3)
+- MCP3208: 4 pairs (CH0/CH1, CH2/CH3, CH4/CH5, CH6/CH7)
+
 ## See Also
 
 - [SPI Bus](/components/spi)