This should speed up pre-commit a bit as only files that are staged will
be processed, and clang-format and shellcheck are only invoked once, not
for every file. When no arguments are given (e.g. on CI), it still uses
'git ls-files'.
This pre-commit config is quite simple: all it does for now is running
the already existing Meta/lint-ci.sh script to ensure no changes that
won't pass the CI linting step are committed.
Consequently pass_filenames is set to false, as these scripts will
determine which files to check themselves - should this ever become a
performance bottleneck, we can update them to accept an optional list of
filenames.
It should be noted that using pre-commit for Serenity development is by
no means a requirement, but doing so may decrease the number of CI
builds failing due to forgotten license headers etc. - especially if
you're pushing to `master` directly, rather than going through pull
requests *hint hint*.
For info how to install & use pre-commit, see https://pre-commit.com/.
Fixes#2365.
