Automate linting for bash files (add to CI).

shellcheck.sh

#!/bin/bash -e

if ! [ -x "$(command -v shellcheck)" ]; then
  echo 'Program ShellCheck not found. Aborting.' >&2
  exit 1
fi

# finds either .sh or .bin files
if find . -type f \( -iname \*.sh -o -iname \*.bin \) -print0 | xargs -n1 -0 shellcheck -s bash; then
    echo -e "ShellCheck lint test passed!"
else
    echo -e >&2 "ShellCheck lint test failed!"
fi