Added index configuration variable entry

[leejoow]

Description:

Add index configuration attribute to reflect component change in documentation

Pull request in esphome with YAML changes (if applicable):

• Dallas indexing esphome#11346

Checklist:

• I am merging into next because this is new documentation that has a matching pull-request in esphome as linked above.
  or

• I am merging into current because this is a fix, change and/or adjustment in the current documentation and is not for a new component or feature.

• Link added in /components/index.rst when creating new documents for new components or cookbook.

New Component Images

If you are adding a new component to ESPHome, you can automatically generate a standardized black and white component name image for the documentation.

To generate a component image:

1. Comment on this pull request with the following command, replacing COMPONENT_NAME with your component name in UPPER_CASE format with underscores (e.g., BME280, SHT3X, DALLAS_TEMP):

   @esphomebot generate image COMPONENT_NAME
   

2. The ESPHome bot will respond with a downloadable ZIP file containing the SVG image.

3. Extract the SVG file and place it in the images/ folder of this repository.

4. Use the image in your component's index table entry in /components/index.rst.

Example: For a component called "DHT22 Temperature Sensor", use:

@esphomebot generate image DHT22

[Copilot]

Pull Request Overview

This PR adds documentation for the new index configuration variable in the Dallas Temperature sensor component, which provides an alternative to using device addresses for identifying sensors on the bus.

• Added index configuration variable documentation
• Updated address variable description to clarify relationship with index
• Added example usage of index in the configuration example

[Copilot]

Grammar error: 'when during startup' should be 'when a sensor is not connected during startup' or 'during startup when a sensor is not connected'.

Suggested change

	- **index** (*Optional*, byte): The index of the sensor. Required if there is more than one device on the bus and address is not specified. *Note this index is based on the hardware addresses of the sensor and indexes will shift when during startup a sensor is not connected.*
	- **index** (*Optional*, byte): The index of the sensor. Required if there is more than one device on the bus and address is not specified. *Note this index is based on the hardware addresses of the sensor and indexes will shift during startup when a sensor is not connected.*

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[ssieb]

Suggested change

	- **index** (*Optional*, byte): The index of the sensor. Required if there is more than one device on the bus and address is not specified. *Note this index is based on the hardware addresses of the sensor and indexes will shift when during startup a sensor is not connected.*
	- **index** (*Optional*, byte): The index (0-based) of the sensor. Required if there is more than one device on the bus and address is not specified.
	*Note this index is based on the hardware addresses of the sensors and the order can be different if any sensors are changed/added/removed.*