Fix esp_http_client example: Set proper server verification by adding the postman root cert for https_async demo

test case.

examples/protocols/esp_http_client/main/CMakeLists.txt

@@ -3,4 +3,5 @@
 # (If this was a component, we would set COMPONENT_EMBED_TXTFILES here.)
 idf_component_register(SRCS "esp_http_client_example.c"
                     INCLUDE_DIRS "."
-                    EMBED_TXTFILES howsmyssl_com_root_cert.pem)
+                    EMBED_TXTFILES howsmyssl_com_root_cert.pem
+                    postman_root_cert.pem)

examples/protocols/esp_http_client/main/esp_http_client_example.c

@@ -38,6 +38,10 @@ static const char *TAG = "HTTP_CLIENT";
 extern const char howsmyssl_com_root_cert_pem_start[] asm("_binary_howsmyssl_com_root_cert_pem_start");
 extern const char howsmyssl_com_root_cert_pem_end[]   asm("_binary_howsmyssl_com_root_cert_pem_end");
 
+extern const char postman_root_cert_pem_start[] asm("_binary_postman_root_cert_pem_start");
+extern const char postman_root_cert_pem_end[]   asm("_binary_postman_root_cert_pem_end");
+
+
 esp_err_t _http_event_handler(esp_http_client_event_t *evt)
 {
     static char *output_buffer;  // Buffer to store response of http request from event handler
@@ -521,6 +525,7 @@ static void https_async(void)
     esp_http_client_config_t config = {
         .url = "https://postman-echo.com/post",
         .event_handler = _http_event_handler,
+        .cert_pem = postman_root_cert_pem_start,
         .is_async = true,
         .timeout_ms = 5000,
     };

examples/protocols/esp_http_client/main/postman_root_cert.pem

@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----