automate generation of default config in the docs

[Remi-Gau]

Is this created automatically or manually?

Originally posted by @marcobarilari in #105 (comment)

[Remi-Gau]

Manually but I can work on some automation because I am already tired of copy pasting twice.

Probably to also reuse in some of our other repos:

• CPP BIDS
• CPP PTB
• CPP SPM
• ...