Find payload.config.cjs automatically

[NEO97online]

Since payload is currently on commonjs still, it's harder to use in projects that use ESM.

If I have module: true in my package.json, I won't be able to use .js as the file extension for my payload config, I'll have to use .cjs. Unfortunately, payload doesn't look for payload.config.cjs, so I then have to specify the PAYLOAD_CONFIG_PATH environment variable for every payload command.

Instead, payload should also search for payload.config.cjs instead of only *.js and *.ts.