Add copyright lint to CI/CD pipeline

[Notgnoshi]

Maybe something like

shopt -s globstar
for source in ./src/**/*.rs; do
    echo "Checking $source for copyright statement"
    should_exit="false"
    if ! head "$source" | grep "// Copyright 2023 Raven Industries inc"; then
        echo "$source missing copyright statement"
        should_exit="true"
    fi
    if [[ "$should_exit" = "true" ]]; then
        echo "Missing copyright statement(s) ..."
        exit 1
    fi
done

but done in a way that contributors can run on their own systems? Maybe a tool to insert them if they're missing?

See 4045ceb for why there's a copyright statement.