Support file-level ignore

[azrsh]

I would like an option to exclude certain workflows from actionlint.
If possible, it would be better to put the option in actionlint.yml or a file like .actionlintignore instead of command line options so that the settings can be managed by Git.

Currently, I avoid this problem by specifying files other than "workflows I want to exclude from lint" on the command line.
If there is already a better way, please let me know.