Feature Request: Add to .gitignore

[chenboshuo]

I think we run

peru reup 

we can search the .gitignore mark

# peru files

and add items to them.

For instance,
if I have the peru.yaml file like:

imports:
  my_silde: notes/

git module my_silde:
  url: git@github.com:chenboshuo/myslide_template.git
  pick: [makefile,myslide.cls]
  rev: cf178c930b5702230fb2dc953873aa202d404aa6

And we setting the setting items in peru.yaml:

settings:
  auto-ignore: true

and I have .gitignore like:

# peru
**/.peru

# peru files

after my run peru reup,
the .gitignore become:

# peru
**/.peru

# peru files
+++ notes/makefile
+++ notes/myslide.cls

Thank you for your attention.