package/bats-file: new package

package/bats-file: new package

bats-file is a helper library providing common filesystem related
assertions and helpers for Bats.

This library does not provide an installer. Manually install the files
under /usr/lib/bats/bats-file which is what the Arch Linux package
does[1]. This makes the library loadable using `bats_load_library`[2].

[1] https://gitlab.archlinux.org/archlinux/packaging/packages/bats-file/-/blob/main/PKGBUILD?ref_type=heads
[2] https://bats-core.readthedocs.io/en/stable/writing-tests.html#bats-load-library-load-system-wide-libraries

Signed-off-by: Brandon Maier <[email protected]>
[[email protected]: move as sub-option of bats-core]
Signed-off-by: Yann E. MORIN <[email protected]>