Accessing buildConfig.custom

I want to use the payload config to configure stuff. How can I access the 'custom' prop of the builConfig within my plugins?

e.g. I want to set a custom bool in my buildConfig:

custom: {

mediaDatePrefix: false,

},

and read that config within my plugin. Is that possible?

if ((await payloadConfig).custom.mediaDatePrefix) {

}

figured it out!