feat: add default environments to platformio.ini to avoid unnecessary build error

Author: GwnDaan

examples/virtual_terminal/esp32_platformio_object_pool/platformio.ini

@@ -7,6 +7,9 @@
 ;
 ; Please visit documentation for the other options and examples
 ; https://docs.platformio.org/page/projectconf.html
+[platformio]
+default_envs = denky32 ; Don't build the CI environment by default, to avoid unnecessary build errors for beginners who select the default environment
+
 [env:denky32]
 platform = espressif32
 board = denky32