--show-gitignored, but do not enter

`broot` allows special paths in the config:
```
special_paths: {
"/media/slow-backup-disk" : no-enter
"/home/dys/useless" : hide
"/home/dys/my-link-I-want-to-explore" : enter
}
```
which are quite useful for dealing e.g. with `.git` folders:
```
special_paths: {
"**/.git": no-enter
}
```
so they are still visible in `broot` (especially when used as a replaced for `tree`), but don't mess the output with their content.

It would be nice to achieve similar effect with git-ignored directores.

Start by locating broot's handling of the `special_paths` configuration and its traversal of git-ignored directories. Compare the requested `no-enter` behavior with the existing `**/.git` example and determine how `--show-gitignored` currently affects directory descent. Done means ignored directories remain visible while their contents are not entered.

Written by the indexing model from the issue text.