Non-blocking HTTP requests for ESP-IDF

The current `http_request` component blocks the main loop while the connection is set up (reading body in `loop()` is possible.)

Claude's take on this is below, I believe it's a decent summary. The additional task is a heavyweight solution, re-implementing using sockets and select() is a big job with significant risks. I did not see anything in newer IDF that changes much, and testing the "async" connect does still block on the initial handshake.

## From Claude.ai

The key is using esp_http_client_perform_async() instead of the blocking esp_http_client_perform(). However, there's an important detail about connection handling:

Non-blocking Connection Setup
For truly non-blocking connection establishment, you need to:

Set the client to non-blocking mode using esp_http_client_set_timeout_ms() with a timeout of 0, or configure it during initialization
Use ESP_HTTP_CLIENT_NON_BLOCKING configuration option (though this isn't always sufficient by itself)
Better Approach: Event-driven with esp_http_client_perform_async()
The async API is designed for this use case:

```c
esp_http_client_config_t config = {
.url = "http://example.com",
.event_handler = http_event_handler,
.timeout_ms = 5000,
};

esp_http_client_handle_t client = esp_http_client_init(&config);

// This returns immediately and continues in background
esp_err_t err = esp_http_client_perform_async(client);
```

However, even with perform_async(), the initial TCP connection and TLS handshake may still block depending on the ESP-IDF version.

Most Reliable Non-blocking Solution
For complete non-blocking behavior including connection setup, consider:

* Run HTTP requests in a separate task - Let connection blocking happen in a dedicated task
* Use the underlying socket APIs with non-blocking sockets and select()/poll()
* Check ESP-IDF version - Newer versions (5.x+) have better async support

The separate task approach is most common in ESP32 applications since it keeps your main application responsive while HTTP operations happen in the background.