FR: make startUrlfor platformio-ide.showHome configurable for PlatformIO under code-server in Docker

[pandel]

Hi!

As described in #4035 it is definitely possible to run PlatformIO under Docker, but with some quirks. You can open the PIO Home directly in code-server, if you go to the Ports tab and hit Preview in Editor for the forwarded port URL, but if you use the Quick Access menu it does not work, because it tries to open the PIO URL without taking the Docker base server path http(s)://<serv.er.name>:<docker_port>/proxy/<pio_port>/ into account.

If this base URL would be configurable, than the integration should work again, even under Docker.

Regards,
Holger