docs: add os related scripts

[franzudev]

While composing my dotfiles and searching around, I've found out this useful feature in twpayne/dotfiles - .chezmoiscripts, but I've found that it is not documented.
I hope this can help.

[bradenhilton]

This isn't correct. Tom controls the execution of these scripts with a .chezmoiignore file.

[franzudev]

Of course I've added those lines in my dotfiles, but forgot about them 😅
If anyone thinks it can be valuable to document this behavior I can add the .chezmoiignore part, let me know.

[twpayne]

If anyone thinks it can be valuable to document this behavior I can add the .chezmoiignore part, let me know.

Yup, although it's a "neat trick" that uses .chezmoiignore rather than any special chezmoi behavior. Please do open a PR that documents this trick -- it should be added to the user guide rather than the reference manual. In the meantime, I'll close this PR.