for example, if user does `import-tree ./_foo`,

explicitly asking to traverse `./_foo`, then results must be
`./_foo/bar.nix` but not `./_foo/_baz.nix`.

that is, filtering occurs only on after-root paths.

* feat: initFilter allows looking other file types, ignore other than /_.

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

instead of always keeping a reference to when the extensions
were added.

* fix: dont break when given paths that are files. filter on them instead.

* Update default.nix

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update checkmate.nix

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fmt

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update README.md

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update README.md

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* feat: Importable import-tree objects.

* fix typo. Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

feat: (addPath) Prepend a path to be filtered as import-tree config.

Allow repeated applications of `filtered`, `matching`, and `mapWith`

fix: README.md: add missing `lib`

Some readme suggestions