Add shellcheck lint

Run shellcheck [1] on the bash files.

[1]: https://www.shellcheck.net/

Signed-off-by: Tim Crawford <tcrawford@system76.com>

scripts/clang-format.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # SPDX-License-Identifier: GPL-3.0-only
 
-FILES=($(git ls-files '*.[ch]'))
+readarray -t FILES < <(git ls-files '*.c' '*.h')
 
 FMT_OPTS=(
     "-style=file"