Provide detailed example of custom component using existing Arduino libraries

**Describe the problem you have/What new integration you would like**
I have some reasonable plain C and OOP python programming skills, but I'm not an expert C++ coder and have been struggling to create custom components based on the existing documentation and DIY examples.

The custom component examples in ESPHome documentation focus on sensors and not outputs like displays, and there are not really any full worked examples to show how to integrate existing Arduino libraries.

I found this when trying to create a custom component for I2C LED display with an existing Adafruit library (refer to this [feature ](https://github.com/esphome/feature-requests/issues/625)request).

I would appreciate a documentation update to provide a more detailed example / tutorial on how to integrate existing Arduino libraries as custom components, and how to call them from yaml.

**Please describe your use case for this integration and alternatives you've tried:**
I've studied the ESPHome custom component documentation, DIY examples, and other custom components but fail to fully grasp how to integrate an existing Arduino library.

**Additional context**
None

Start with the ESPHome custom component documentation, DIY examples, and existing custom components, focusing on the Adafruit I2C LED display library use case. Done means adding a full worked example or tutorial that explains integrating an existing Arduino library and calling the custom component from YAML, including an output such as a display.

Written by the indexing model from the issue text.