Allow to exclude types of warnings

[kenorb]

$  shellcheck -h
...
  -e CODE1,CODE2..    --exclude=CODE1,CODE2..    Exclude types of warnings

E.g. shellcheck -e SC1004,SC1083 ...

[kenorb]

As per ludeeus/action-shellcheck/issues/5, I think it's possible to use environments instead. E.g. SHELLCHECK_OPTS.

See https://www.mankier.com/1/shellcheck.

[Azbagheri]

@kenorb thanks for your interest in our action and the feature request. We will surely consider that in our next release!