Update httpd_parse.c

More comments.

components/esp_http_server/src/httpd_parse.c

@@ -1078,7 +1078,9 @@ esp_err_t httpd_req_get_hdr_value_str(httpd_req_t *r, const char *field, char *v
             val_ptr++;
         }
 
-        /* Get the NULL terminated value and copy it to the caller's buffer. */
+        /* Get the NULL terminated value and copy it to the caller's buffer.
+         * Note `strlcpy()` will always return the size of the source string
+         * including terminimating null.*/
         size_t full_size = strlcpy(val, val_ptr, val_size);
 
         /* If buffer length is smaller than needed, return truncation error */