docs: add comprehensive README with GPIO plugin documentation

README.md

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+# Sprocket GPIO Plugin
+
+A comprehensive GPIO plugin for the Sprocket framework, providing support for various input and output configurations on ESP8266 and ESP32 devices.
+
+## Overview
+
+The GPIO plugin extends Sprocket-Core with flexible GPIO management capabilities, supporting multiple input types and configurations for IoT sensor applications.
+
+## Features
+
+- **Multiple Input Types**: Analog, digital, audio, and PIR sensor support
+- **Configurable Pins**: Flexible pin assignment and mode configuration
+- **Event-Driven**: Publishes sensor data to configurable topics
+- **Task-Based**: Integrated with Sprocket's task scheduler
+- **Cross-Platform**: Supports both ESP8266 and ESP32
+
+## Supported Input Types
+
+### Analog Inputs
+- Configurable threshold detection
+- Update interval control
+- Topic-based event publishing
+
+### Digital Inputs
+- Digital pin state monitoring
+- Event-driven state changes
+- Configurable pin modes
+
+### Audio Inputs
+- Audio signal processing
+- Threshold-based detection
+- Real-time audio monitoring
+
+### PIR Motion Sensors
+- Motion detection
+- Configurable sensitivity
+- Event publishing on motion
+
+## Configuration
+
+```cpp
+struct GpioConfig {
+    int pin;              // GPIO pin number
+    int threshold;        // Detection threshold
+    int updateInterval;   // Update frequency in ms
+    const char *topic;    // Event topic for publishing
+    int pinMode;          // Pin mode (INPUT, INPUT_PULLUP, etc.)
+};
+```
+
+## Usage Example
+
+```cpp
+#include <GpioConfig.h>
+#include <AnalogInputPlugin.h>
+
+// Configure analog input
+GpioConfig analogConfig = {
+    .pin = A0,
+    .threshold = 512,
+    .updateInterval = 1000,
+    .topic = "sensor/analog",
+    .pinMode = INPUT
+};
+
+// Create and activate plugin
+AnalogInputPlugin analogPlugin(analogConfig);
+analogPlugin.activate(scheduler);
+```
+
+## Installation
+
+1. Include the plugin in your Sprocket project
+2. Configure GPIO pins according to your hardware setup
+3. Initialize plugins with appropriate configurations
+4. Activate plugins through the Sprocket scheduler
+
+## Dependencies
+
+- Sprocket-Core framework
+- Arduino framework
+- TaskScheduler library
+
+## Platform Support
+
+- ESP8266
+- ESP32
+
+## Examples
+
+See the `examples/` directory for complete usage examples:
+- `analog/` - Analog input configuration
+- `audio/` - Audio input processing
+- `combined/` - Multiple input types
+- `pir/` - Motion sensor setup
+- `rotary/` - Rotary encoder support
+
+## License
+
+See LICENSE file for details.